<PAGE>   1

                                                                   EXHIBIT 10.11

                                                                    CONFIDENTIAL


                            SIBIA NEUROSCIENCES, INC.
                              AMENDED AND RESTATED
                        MANAGEMENT CHANGE-OF-CONTROL PLAN

                  AMENDED AND RESTATED AS OF DECEMBER 10, 1998

                                  INTRODUCTION

        This SIBIA Neurosciences, Inc. (formerly, "The Salk Institute
Biotechnology/Industrial Associates, Inc."), a Delaware corporation (the
"Company"), Management Change-of-Control Plan (the "Plan") was adopted by the
Board of Directors (the "Board") of the Company, effective November 10, 1994.
The Plan is intended to provide members of management who are Participants in
the Plan with the Benefits specified herein in the event of a Change of Control.

        WHEREAS, the Plan was previously amended by the Board in November 1995,
March 1996 and June 1997 and amended and restated on February 26, 1998 (the
"Prior Amendments");

        WHEREAS, the Board wishes to amend and restate the Plan to include
Stephen F. Keane as a Plan participant, to exclude former Plan participants, and
to provide participants with severance benefits in the event of certain
transactions not currently contemplated or provided for in the Plan and to
provide for administrative ease.

        NOW, THEREFORE, upon authorization duly granted by the Board, the
undersigned parties hereto agree to amend and restate the Plan as provided
herein.

        Certain capitalized terms used in the Plan are defined in Article 13.

                                    ARTICLE 1

                    ESTABLISHMENT OF THE PLAN AND ELIGIBILITY

        1.1 ESTABLISHMENT OF PLAN. As of the Effective Date, the Company hereby
establishes a plan to be known as the "Management Change-of-Control Plan" (the
"Plan"), as set forth herein.

        1.2 APPLICABILITY OF PLAN. The benefits provided by the Plan shall be
available to all Participants, unless otherwise specifically provided.




                                       1.
<PAGE>   2

                                    ARTICLE 2

                                   ELIGIBILITY

        2.1 PARTICIPATION. William T. Comer will be a Participant in the Plan
and will serve in the position of Chief Executive Officer. Jeffrey McKelvy will
be a Participant in the Plan and will serve in the position of Executive Vice
President. The following members of management shall also be Participants in the
Plan and shall each serve in a position of Vice President: Stephen F. Keane, G.
Kenneth Lloyd, Ian A. McDonald, David E. McClure, and Thomas A. Reed. The Board
or the Compensation Committee of the Board (the "Compensation Committee") may,
in its sole discretion, designate additional members of management or employees
to be Participants in the Plan and, subject to the terms of Section 2.2, may
decide that members of management or employees who have been designated as
Participants in the Plan shall no longer be Participants.

        2.2 DURATION OF PARTICIPATION. A Participant shall cease to be a
Participant in the Plan upon a determination thereof by the Board or the
Compensation Committee; provided, however, that in no event shall any such
determination impair a Participant's rights under this Plan with respect to
Benefits that have accrued prior to such determination. Without limiting the
foregoing, if a Participant is then entitled to payment of Benefits as a result
of a Change of Control that occurred prior to such determination, such
Participant shall remain a Participant in the Plan until the full amount of such
Benefits has been paid to such Participant. In no event shall any Participant be
entitled to Benefits pursuant to this Plan with respect to a Change of Control
that occurs after the termination of such Participant's employment with the
Company, for any reason or for no reason, and nothing in this Plan shall alter
the status of each Participant as an at-will employee of the Company.

                                    ARTICLE 3

                                    BENEFITS

        Participants shall be entitled to the following Benefits pursuant to
this Plan: Bonus Payments, as provided in Article 4; Stock Options, as provided
in Article 5 (except Dr. David McClure, Dr. Jeffrey McKelvy, and Stephen F.
Keane shall not be entitled to any benefits provided to Plan Participants under
Article 5); and Severance Benefits, as provided in Article 6.

                                    ARTICLE 4

                                 BONUS PAYMENTS

        4.1 BONUS PAYMENT UPON CHANGE OF CONTROL. If a Change of Control occurs,
then each Participant (i) who remains employed by the Company or its successor
for a period of six months following such Change of Control (the "Bonus Service
Period") or (ii) whose employment shall be Terminated Without Cause (including
without limitation and as defined in Section 13.12, a reduction of the
Participant's rate of compensation or a change in Participant's
responsibilities, authority, titles or offices) during the Bonus Service Period,
shall receive a 



                                       2.
<PAGE>   3

Bonus Payment based upon the Company's valuation at the time of the Change of
Control in accordance with the following schedule:


<TABLE>
             VALUE OF COMPANY                                  BONUS AMOUNT AS A
           UPON CHANGE OF CONTROL                            PERCENT OF BASE SALARY
<S>                                                          <C>
         Less than $10,000,000                                          0%
         $10,000,000 to $20,000,000                                    10%
         Greater than $20,000,000                                      25%
</TABLE>


        4.2 DETERMINATION OF VALUE OF THE COMPANY. For purposes of determining
the Bonus amounts to be paid under this Article 4 and the number of Stock
Options under Article 5, the value of the Company shall be determined as of the
closing date of the applicable Change of Control transaction (the "Value
Determination Date ") and shall be equal to the market capitalization of the
Company immediately prior to such closing.

        4.3 TIME OF BONUS PAYMENT. The Bonus Payments under this Article 4 shall
be paid in a cash lump sum no later than fifteen (15) days following the
earliest of (i) the Bonus Completion Date, or (ii) the date the Participant's
employment is Terminated Without Cause.

                                    ARTICLE 5

                       STOCK OPTIONS AND OTHER INCENTIVES

        5.1 STOCK OPTIONS. Participants (except Dr. David McClure, Dr. Jeffrey
McKelvy, and Stephen F. Keane who shall not be entitled to any benefits provided
under this Article 5) shall receive a one-time grant of nonqualified stock
options to acquire the Company's common stock ("Stock Options"). The number of
such Stock Options granted shall be based upon the Participant's position with
the Company on the date the Participant is initially designated as a Participant
by the Board or the Compensation Committee and in accordance with the schedule
set forth in this Section 5.1. Notwithstanding the foregoing, in the event the
Board or Compensation Committee subsequently promotes a Participant (other than
Dr. David McClure, Dr. Jeffrey McKelvy, or Steven F. Keane) to a more senior
officer position, such Participant shall be entitled to receive an additional
grant of Stock Options in an amount equal to that required to make the total
Stock Options granted to such Participant equal to that number of Stock Options
granted to other Participants serving in like positions with the Company. Each
Stock Option granted under this Article 5 shall have an exercise price of $2.00
per share (which price does not reflect the 2.35-to-1 reverse stock split
effected by the Company in May of 1996). Each Stock Option shall not be granted
pursuant to the Company's Amended and Restated 1992 Stock Option and Restricted
Stock Plan, but shall incorporate the terms of such plan to the extent not
inconsistent with this Plan, as determined by the Board or the Compensation
Committee in its sole discretion, including terms related to the transferability
of stock options granted hereunder.




                                       3.
<PAGE>   4

<TABLE>
OFFICER STATUS WITH COMPANY                       NUMBER OF STOCK
                                                  OPTIONS GRANTED
<S>                                               <C>

Vice President                                    25,000 shares
Chief Executive Officer (CEO)                     40,000 shares
</TABLE>


        5.2 TIME AND EXERCISE OF STOCK OPTION GRANT. The Stock Options granted
under this Article 5 shall be granted as of the Effective Date or, if later, the
date the Participant is initially designated as a Participant by the Board or
the Compensation Committee; provided that Stock Options granted to a Participant
by reason of the promotion of such Participant to a more senior officer position
pursuant to Section 5.1 shall be granted as of the effective date of such
promotion. Except as set forth below, the Stock Options granted under this
Section 5 shall be subject to vesting and shall not become exercisable in any
respect until seven (7) years following the date of grant, at which time they
shall become fully vested and exercisable pursuant to the terms thereof.
Notwithstanding the foregoing, in the event that at any time subsequent to the
Effective Date the Company shall consummate an initial public offering of its
Common Stock, 25% of all then outstanding options under the Plan shall vest and
become fully exercisable immediately prior to the effective date of the
registration statement pursuant to which such shares of Common Stock are being
registered, with the remaining 75% of the then outstanding options vesting in
three equal annual installments commencing on the anniversary date of the
effectiveness of the registration statement. In addition to the foregoing,
vesting of options outstanding under the Plan shall be accelerated and the Stock
Options will become fully vested and exercisable pursuant to their terms
effective immediately prior to a Change of Control.

        Stock Options granted to each eligible Participant hereunder shall be
exercisable for not more than thirty (30) days following such Participant's
termination of employment (for any reason or for no reason) and shall also be
subject to the terms and conditions specified in a standard form of stock option
agreement as set forth in Appendix A.

                                    ARTICLE 6

                               SEVERANCE BENEFITS

        6.1 RIGHT TO SEVERANCE BENEFITS. Each Participant shall be entitled to
receive Severance Benefits from the Company as set forth in Section 6.2 in the
event such Participant is Terminated Without Cause at any time during the period
commencing one (1) month before and ending thirteen (13) months after the
effective date of a Change of Control.

        6.2 DETERMINATION OF SEVERANCE BENEFITS. Severance Benefits payable
pursuant to Section 6.1 shall be determined as follows:

               (a) Each Vice-President and Executive Vice-President
participating in the Plan will receive as a Severance Payment the equivalent of
one and one-half (1 1/2) times Base 


                                       4.
<PAGE>   5

Salary and his or her prorated annual bonus. The Chief Executive Officer (CEO)
will receive as a Severance Payment the equivalent of two (2) times Base Salary
and his or her prorated annual bonus.

               (b) The Company shall pay the premiums for the terminated
Participant and for the eligible spouse and other COBRA qualified beneficiaries
of the terminated Participant for the health insurance continuation benefits
provided under the Consolidated Omnibus Budget Reconciliation Act of 1985, as
amended ("COBRA"), and Section 4980B of the Internal Revenue Code of 1986, as
amended (the "Code"), for the maximum period provided by law for such qualified
beneficiary's COBRA continuation rights.

               (c) The Company shall reimburse the Participant for outplacement
expenses incurred during the three months following the Date of Termination as a
result of the Participant's search for other employment. In no event, however,
will such outplacement expenses exceed a total of seven thousand five hundred
dollars ($7,500) per Participant. The Participant shall provide to the Company
proof of such outplacement expenses in a form mutually acceptable to the Company
and the Participant.

        6.3 TIME OF SEVERANCE PAYMENT. The Severance Payment shall be paid in
lump sum in cash not later than thirty (30) days following the Date of
Termination.

        6.4 NO MITIGATION. The Participant shall not be required to mitigate the
amount of the Severance Benefits by seeking other employment or otherwise, and
any amount earned by the Participant as the result of employment by another
employer after the Date of Termination shall not reduce the amount of the
Severance Payment.

        6.5 WITHHOLDING. The Company shall withhold appropriate federal, state,
local and foreign income and employment taxes from any payments hereunder.

        6.6 NOTICE OF TERMINATION. Any termination by the Company for Cause or
by the Participant for Good Reason shall be communicated by Notice of
Termination to the other party hereto given by hand delivery or by registered or
certified mail, return receipt requested, postage prepaid, if to the
Participant, to the Participant at the Participant's address as set forth in the
Company's records, and, if to the Company, to SIBIA, 505 Coast Boulevard South,
La Jolla, California 92037-4641, or to such other address as may be designated
by the Company. Any notices given pursuant to this Section 6.6 shall be
effective on the earlier of the date on which such notice is actually received
by the addressee or the date that is three days after such notice is sent by the
addressor. For purposes of the Plan, a "Notice of Termination" means a written
notice which (i) indicates the provisions in the Plan that are affected by such
termination and (ii) if the Date of Termination, as defined below, is other than
the date of receipt of such notice, specifies the termination date (which date
shall be not more than fifteen (15) days after the giving of such notice). The
failure by the Company or the Participant to set forth in the Notice of
Termination any fact or circumstance which contributes to a showing of Cause or
of Good Reason shall not waive any right of the Company or of the Participant,
respectively, hereunder or 



                                       5.
<PAGE>   6

preclude the Company or the Participant, respectively, from asserting such fact
or circumstance in enforcing its or his rights hereunder.

        6.7 DATE OF TERMINATION. "Date of Termination" means the date of receipt
of the Notice of Termination or any later date specified therein, as the case
may be; provided, however, that (i) if the Participant's employment terminates
by the Company other than by reason of death or Disability, or for Cause, the
Date of Termination shall be the date on which the Company notifies the
Participant of such termination and (ii) if the Participant's employment is
terminated by reason of death or Disability, the Date of Termination shall be
the date of death or determination of termination of employment on account of
Disability pursuant to Section 13.9, as the case may be.

        6.8 CERTAIN REDUCTION OF PAYMENTS. In the event that any distribution
received or to be received by a Participant pursuant to the Plan
("Distribution") would (i) constitute a "parachute payment" within the meaning
of Section 280G of the Code and (ii) be subject to the excise tax imposed by
Section 4999 of the Code (the "Excise Tax"), then such Distribution shall be
reduced to the largest amount which would result in no portion of the
Distribution being subject to the Excise Tax or such Distribution may be paid in
full, whichever produces the better after-tax result for the Participant.
Necessary calculations will be prepared by a mutually acceptable accounting
firm.

                                    ARTICLE 7

                          PAYMENTS TO AND FROM THE PLAN

        The cash benefits under the Plan shall be paid from the general funds of
the Company (by certified or official bank check or wire transfer of immediately
available funds to an account designated by the applicable Participant), and the
Participants shall be no more than unsecured general creditors of the Company.

                                    ARTICLE 8

                     OTHER RIGHTS AND BENEFITS NOT AFFECTED

        8.1 NONEXCLUSIVITY. Nothing in the Plan shall prevent or limit any
Participant's continuing or future participation in any benefit, bonus,
incentive or other plans, programs, policies or practices provided by the
Company and for which a Participant may otherwise qualify, nor shall anything
herein limit or otherwise affect such rights as any Participant may have under
any stock option or other agreements with the Company. Except as otherwise
expressly provided herein, amounts which are vested benefits or which a
Participant is otherwise entitled to receive under any plan, policy, practice or
program of the Company at or subsequent to the Date of Termination shall be
payable in accordance with such plan, policy, practice or program.



                                       6.
<PAGE>   7

        8.2 EMPLOYMENT STATUS. The Plan does not constitute a contract of
employment or impose on any Participant or the Company any obligation to retain
any Participant as an employee, to change the status of the Participant's
employment, or to change the Company's policies regarding termination of
employment. In no event shall any Participant be entitled to Benefits pursuant
to this Plan with respect to a Change of Control that occurs after the
termination of such Participant's employment with the Company, for any reason or
for no reason, and nothing in this Plan shall alter the status of each
Participant as an at-will employee of the Company.

                                    ARTICLE 9

                              SUCCESSOR TO COMPANY

        The Plan shall be binding upon any successor or assignee, whether direct
or indirect, by purchase, merger, consolidation or otherwise, to all or
substantially all the business or assets of the Company, and any such successor
or assignee shall be required to perform the Company's obligations under the
Plan, in the same manner and to the same extent that the Company would be
required to perform if no such succession or assignment had taken place. In such
event, the term "Company," as used in the Plan, shall mean the Company as
hereinafter defined and any successor or assignee to the business or assets
which by reason hereof becomes bound by the terms and provisions of the Plan.

                                   ARTICLE 10

          DURATION, AMENDMENT AND TERMINATION; RIGHT TO INTERPRETATION

        10.1 DURATION. Beginning on December 31, 1995, and on each subsequent
anniversary of such date, one year shall be added to the term of the Plan,
unless, prior to such date or anniversary, the Company, by resolution of the
Board, shall have notified each Participant in writing that such extension will
not become effective. If such resolutions are adopted by the Board, the term of
the Plan will not be extended and the Plan will terminate on the December 31 on
or following the first anniversary date of the date that such resolutions are
adopted. No termination of the Plan will occur any earlier than thirteen (13)
months following the Change of Control. Notwithstanding the foregoing, the Plan
shall not terminate or expire with respect to any Participant who becomes
entitled to Benefits hereunder until such Participant has received such payments
or other rights in full.

        10.2 NO AMENDMENT OR TERMINATION. Except as set forth in Section 10.1
above, the Company may not change or terminate this Plan with respect to any
Participant without the written consent of such Participant.

        10.3 EXCLUSIVE DISCRETION. The Company shall have the exclusive
discretion and authority to establish rules, forms and procedures for the
administration of the Plan, and to construe and interpret the Plan and to decide
any and all questions of fact, interpretation, definition, computation or
administration arising in connection with the operation of the Plan, 



                                       7.
<PAGE>   8

including, but not limited to, the eligibility to participate in the Plan and
amount of benefits paid under the Plan. The rules, interpretations, computations
and other actions of the Company shall be binding and conclusive on all persons.

                                   ARTICLE 11

                            NON-TRANSFER OF BENEFITS

        No benefit hereunder shall be subject to anticipation, alienation, sale,
transfer, assignment, pledge, encumbrance or charge, and any attempt to do so
shall be void.

                                   ARTICLE 12

                       LEGAL CONSTRUCTION AND ARBITRATION

        12.1 APPLICABLE LAW. This Plan shall be construed in accordance with the
laws of the State of California without regard to the conflict of laws
provisions thereof.

        12.2 ARBITRATION. Any and all disputes or controversies, whether of law
or fact of any nature whatsoever, arising from or respecting the application of
the Plan to any Participant shall be decided by arbitration by the American
Arbitration Association in accordance with the rules and regulations of that
Association, or by any other arbitration body mutually agreed upon by the
parties. Pre-arbitration discovery shall be permitted at the request of either
party to a dispute under appropriate protection for proprietary and confidential
business information.

        The arbitrators shall be selected as follows: the Company and the
Participant who is a party to the dispute shall each select one independent,
qualified arbitrator and the two arbitrators so selected shall select the third
arbitrator. The Company reserves the right to disqualify any individual
arbitrator who shall be employed by or affiliated with a competing organization.
The Company will pay all of the costs of any arbitrator hired to resolve a
dispute as determined by the American Arbitration Association.

        Arbitration shall take place in San Diego County, California, or any
other location mutually agreeable to the parties. At the request of either
party, arbitration proceedings will be conducted in the utmost secrecy and, in
such case, all documents, testimony and records shall be received, heard and
maintained by the arbitrators in secrecy under seal, available for inspection
only by the parties to the arbitration, their respective attorneys, and their
respective expert consultants or witnesses who shall agree, in advance and in
writing, to receive all such information confidentially and to maintain such
information in secrecy, and make no use of such information except for the
purposes of the arbitration, until such information shall become generally
known.

        The arbitrators, who shall act by majority vote, shall be able to decree
any and all relief of an equitable nature, including but not limited to such
relief as a temporary restraining order, a temporary injunction, or a permanent
injunction, and shall also be able to award damages, with 



                                       8.
<PAGE>   9

or without an accounting and costs. The decree or judgment of an award rendered
by the arbitrators may be entered and enforced in any court having jurisdiction
over the parties.

        Reasonable notice of the time and place of arbitration shall be given to
persons other than the parties, if such notice is required by law, in which case
such persons or their authorized representatives shall have the right to attend
or participate in the arbitration hearing in such manner as the law shall
require.

        If any action is necessary to enforce or interpret the application of
the Plan to a Participant, then that Participant shall be entitled to reasonable
attorneys fees, costs, and necessary disbursements in addition to any other
relief to which that Participant may be entitled, if any, under all
circumstances regardless of the outcome of the action.

                                   ARTICLE 13

                                   DEFINITIONS

        For purposes of the Plan, the following terms shall have the meanings
set forth below.

        13.1 "BASE SALARY" means, as of December 10, 1998 (or if the individual
named below became a participant in the Plan following December 10, 1998, the
date as of which such individual first became a Participant), the following
salaries for each Participant: William T. Comer, $280,000; Stephen F. Keane,
$150,000; G. Kenneth Lloyd, $200,000; Ian A. McDonald, $173,000; David E.
McClure, $170,000; Thomas A. Reed; $165,000 and Jeffrey McKelvy, $250,000. The
Base Salary for each Participant or any Participant may be increased by the
Compensation Committee in its sole discretion and such increased Base Salary in
effect on the Value Determination Date shall constitute Base Salary for purposes
of payments under the Plan.

        13.2 "BENEFITS" means, collectively, the various benefits payable or
awarded under this Plan, which are the Bonus Payments, the Stock Options, and
the Severance Benefits.

        13.3 "BONUS COMPLETION DATE" means the last date of the Bonus Service
Period.

        13.4 "BONUS PAYMENTS" means the payments described in Article 4.

        13.5 "BONUS SERVICE PERIOD" shall have the meaning assigned in Section
4.1 herein.

        13.6 "CAUSE" means (a) gross or habitual failure to perform assigned
duties of the Participant's job, that is, performance failure not corrected
within thirty (30) days after written notice to the Participant thereof or (b)
misconduct, including but not limited to: (i) conviction of a crime, or entry of
a plea of nolo contendere, with regard to a crime involving moral turpitude or
dishonesty, (ii) illegal drug use or alcohol abuse on Company premises or at a
Company sponsored event, (iii) conduct by the Participant which in the good
faith and reasonable determination by two-thirds (2/3) of the Board demonstrates
gross unfitness to serve, or (iv) intentional, material violation by the
Participant of any contract between the Participant and the Company or any
statutory duty of the Participant to the Company.



                                       9.
<PAGE>   10

               Provided that in the event that any of the events described in
(iii) above may be cured, the Company shall provide written notice to the
Participant describing the nature of such event and the Participant shall
thereafter have thirty (30) days to cure such event.

        13.7   "CHANGE OF CONTROL" means any one of the following:

               (a) a sale of all or substantially all of the assets of the 
Company;

               (b) a merger or consolidation in which the Company is not the
surviving corporation (other than a transaction the principal purpose of which
is to change the state of the Company's incorporation or a transaction in which
the voting securities of the Company are exchanged for beneficial ownership of
at least 50% of the voting securities of the controlling acquiring corporation);

               (c) a merger or consolidation in which the Company is the
surviving corporation and less than 50% of the voting securities of the Company
which are outstanding immediately after the consummation of such transaction are
beneficially owned, directly or indirectly, by the persons who owned such voting
securities immediately prior to such transaction;

               (d) any transaction or series of related transactions after which
any person (as such term is used in Section 13(d)(3) of the Securities Exchange
Act of 1934, as amended), other than any employee benefit plan (or related
trust) sponsored or maintained by the Company or any subsidiary of the Company,
becomes the beneficial owner of voting securities of the Company representing
50% or more of the combined voting power of all of the voting securities of the
Company.

               (e) during any period of two consecutive years, individuals who
at the beginning of such period constitute the membership of the Company's Board
of Directors ("Incumbent Directors") cease for any reason to have authority to
cast at least a majority of the votes which all directors on the Board of
Directors are entitled to cast, unless the election, or the nomination for
election by the Company's stockholders, of a new director was approved by a vote
of at least two-thirds of the votes entitled to be cast by the Incumbent
Directors, in which case such director shall also be treated as an Incumbent
Director in the future; or

               (f) the liquidation or dissolution of the Company.

        13.8 "COMPANY" means SIBIA Neurosciences, Inc., a Delaware corporation,
and any successor as provided in Article 9 hereof.

        13.9 "DATE OF TERMINATION" has the meaning set forth in Section 6.7.

        13.10 "DISABILITY" means that the Participant has exhausted any
short-term disability benefits to which he is entitled and is permanently
unable, by reason of a physical or mental incapacity, to perform the normal
duties of the work for which he was employed by the Company.



                                      10.
<PAGE>   11

        13.11 "EFFECTIVE DATE" shall mean November 10, 1994.

        13.12 "GOOD REASON" means any action taken by the Company or its
successor, as the case may be, that results in a (i) reduction of the
Participant's rate of compensation as in effect immediately prior to the Change
of Control, (ii) failure to provide a package of welfare benefit plans which,
taken as a whole, provide substantially similar benefits to those in which the
Participant is entitled to participate immediately prior to the Change of
Control (except that employee contributions may be raised to the extent of any
cost increases imposed by third parties) or any action by the Company which
would adversely affect the Participant's participation or reduce the
Participant's benefits under any of such plans, (iii) change in the
Participant's responsibilities, authority, titles or offices resulting in
diminution of position, excluding for this purpose an isolated, insubstantial
and inadvertent action not taken in bad faith which is remedied by the Company
promptly after notice thereof is given by the Participant, (iv) request that the
Participant relocate to a worksite that is more than 35 miles from his prior
worksite, unless the Participant accepts such relocation opportunity, (v)
material reduction in duties, (vi) failure or refusal of the successor company
to assume the Company's obligations under this Plan, as required by Article 9,
or (vii) material breach by the Company or any successor company of any of the
material provisions of the Plan.

        13.13 "NOTICE OF TERMINATION" has the meaning set forth in Section 6.6.

        13.14 "PARTICIPANT" shall mean an employee who has been designated as a
Participant as provided in Section 2.1.

        13.15 "PLAN" has the meaning set forth in Section 1.1.

        13.16 "SEVERANCE BENEFITS" has the meaning set forth in Section 6.2.

        13.17 "SEVERANCE PAYMENT" has the meaning set forth in Section 6.2.

        13.18 "STOCK OPTIONS" means the options to purchase Company stock
described in Article 5.

        13.19 "TERMINATED WITHOUT CAUSE" shall occur if a Participant's
employment with the Company:

               (a) shall be involuntarily terminated, unless the Company
terminates the employment of the Participant for Cause, or unless the
Participant's employment is terminated by reason of death or Disability; or

               (b) shall be voluntarily terminated by the Participant for Good
Reason.



                                      11.
<PAGE>   12

                                   ARTICLE 14

                                  MISCELLANEOUS

        14.1 SEVERABILITY. If any term, provision, covenant or restriction of
the Plan is held by a court of competent jurisdiction or other authority to be
invalid, void or unenforceable, the remainder of the terms, provisions,
covenants and restrictions of the Plan shall remain in full force and effect and
shall in no way be affected, impaired or invalidated.

        14.2 CONSTRUCTION OF PLAN. Any gender, where appearing in the Plan,
shall be deemed to include the other gender, the singular shall include the
plural, and the plural shall include the singular, unless the context otherwise
requires. Descriptive headings of the several Articles of the Plan are inserted
for convenience only and shall not control or affect the meaning or construction
of any of the provisions hereof. In the event of a conflict between the text of
the Plan and any summary, description or other information regarding the Plan,
the text of the Plan shall control.

        14.3 ADJUSTMENTS TO STOCK. If any change is made in the stock subject to
options granted under the Plan (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 number of shares remaining subject
to such options will be appropriately adjusted in the type(s) and maximum
number. Such adjustments shall be made by the Board or the Compensation
Committee of the Board, the determination of which 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".)

                                   ARTICLE 15

                          CLAIMS, INQUIRIES AND APPEALS

        15.1 APPLICATIONS FOR BENEFITS AND INQUIRIES. Any application for
benefits, inquiries about the Plan or inquiries about present or future rights
under the Plan must be submitted to the Plan Administrator in writing. The
Company, or any successor, shall at all times maintain a Plan Administrator, and
shall give each Participant written notice of any change in the Plan
Administrator or the address to which benefits or inquiries should be sent. The
Plan Administrator is:

                             SIBIA Neurosciences, Inc.
                             Attention: Treasurer
                             505 Coast Boulevard South
                             La Jolla, CA 92037-4641



                                      12.
<PAGE>   13

        15.2 DENIAL OF CLAIMS. In the event that any application for benefits is
denied in whole or in part, the Plan Administrator must notify the applicant, in
writing, of the denial of the application. The written notice of denial will be
set forth in a manner designed to be understood by the Participant, and will
include specific reasons for the denial, specific references to the Plan
provision upon which the denial is based and a description of any information or
material that the Plan Administrator needs to complete the review. This written
notice will be given to the employee within 20 days after the Plan Administrator
receives the application.

        15.3 LEGAL ACTION. No legal action for benefits under the Plan may be
brought until the claimant (i) has submitted a written application for benefits
in accordance with the procedures described by Section 15.1 above and (ii) has
been notified by the Plan Administrator that the application is denied (or the
application is deemed denied due to the Plan Administrator's failure to act on
it within the established time period).

                                   ARTICLE 16

                             OTHER PLAN INFORMATION

        16.1 EMPLOYER AND PLAN IDENTIFICATION NUMBERS. The Employer
Identification Number assigned to the Company (which is the "Plan Sponsor" as
that term is used in ERISA) by the Internal Revenue Service is 95-3616229. The
Plan Number assigned to the Plan by the Plan Sponsor pursuant to the
instructions of the Internal Revenue Service is 530.

        16.2 ENDING DATE FOR PLAN'S FISCAL YEAR. The date of the end of the
fiscal year for the purpose of maintaining the Plan's records is December 31.

        16.3 AGENT FOR THE SERVICE OF LEGAL PROCESS. The agent for the service
of legal process with respect to the Plan is: SIBIA Neurosciences, Inc., 505
Coast Boulevard South, La Jolla, CA 92037-4641, Attn: Treasurer. Service of
legal process also may be made upon the Plan Administrator.

        16.4 PLAN SPONSOR AND ADMINISTRATOR. The "Plan Sponsor" and the "Plan
Administrator" of the Plan is SIBIA Neurosciences, Inc., 505 Coast Boulevard
South, La Jolla, CA 92037-4641. The Plan Sponsor's and Plan Administrator's
telephone number is (619) 452-5892. The Plan Administrator is the named
fiduciary charged with the responsibility for administering the Plan.



                                      13.
<PAGE>   14

                                   ARTICLE 17

                                    EXECUTION

        Having been originally adopted by the Board on November 10, 1994, and
having been amended, this Amended and Restated Management Change of Control Plan
is executed by a duly authorized officer and the Chairman of the Board as of the
26th day of February, 1998.

                                SIBIA NEUROSCIENCES, INC.



                                By:
                                   -----------------------------------------
                                       William T. Comer,
                                       Chief Executive Officer

                                By:
                                   -----------------------------------------
                                       William R. Miller,
                                       Chairman of the Board

                                PARTICIPANTS:


                                William T. Comer
                                --------------------------------------------


                                Stephen F. Keane
                                --------------------------------------------


                                G. Kenneth Lloyd
                                --------------------------------------------


                                David E. McClure
                                --------------------------------------------


                                 Ian A. McDonald
                                --------------------------------------------


                                 Jeffrey McKelvy
                                --------------------------------------------


                                 Thomas A. Reed
                                --------------------------------------------



                                      14.