[***] CONFIDENTIAL TREATMENT REQUESTED
                          REDACTED FOR CONFIDENTIALITY


                              AMENDMENT NUMBER ONE
                              TO AGREEMENT BETWEEN
                        NEUROCRINE BIOSCIENCES, INC. AND
                           JANSSEN PHARMACEUTICA, N.V.


AMENDMENT  NUMBER  ONE  dated  September  24,  1999  (this  "Amendment")  to the
Agreement  effective  as of January 1, 1995 (the  "Original  Agreement")  by and
between  Neurocrine  Biosciences,  Inc., a Delaware  corporation  with principle
offices  located at 10555 Science  Center  Drive,  San Diego,  California  92121
("Neurocrine") and Janssen  Pharmaceutica,  N.V., a corporation  organized under
the laws of Belgium with principle  offices  located at  Turnhoutseweg  30, 2340
Beerse, Belgium ("Janssen").

WHEREAS,  pursuant  to the  Original  Agreement,  Janssen  and  Neurocrine  have
conducted    a    collaborative    research    program    in   the    field   of
corticotropin-releasing factor (CRF) Receptor Antagonists (as defined below) and
have developed certain technology in this field.

WHEREAS,  the Research (as defined  below)  conducted by Neurocrine  and Janssen
pursuant  to the  Original  Agreement  has  led to  filing  of  patents  and the
identification  of certain CRF  Receptor  Antagonist  pre-clinical  and clinical
development candidate compounds.

WHEREAS, Research Term (as defined in the Original Agreement) expired on January
1, 1998 and Janssen and Neurocrine now wish to conduct an additional  program of
collaborative  research  (the  "Back-up  Program")  designed to identify new CRF
Receptor Antagonist which will be subject to the terms of the Original Agreement
as amended hereby.

NOW, THEREFORE,  in consideration of the promises and mutual covenants contained
herein,  and  for  other  good  and  valuable  consideration,  the  receipt  and
sufficiency  of which are  hereby  acknowledged,  the  parties  hereto  agree as
follows:

                                    ARTICLE 1
                                   DEFINITIONS

Defined Terms.  Capitalized  terms used herein that are not defined herein shall
have the meanings assigned to such terms in the Original Agreement.

1.1 "Amendment Effective Date" shall mean April 15, 1999.

1.2 "Back-up PCC" shall mean any  composition of matter that (or, in the case of
prodrugs, an active ----------- metabolite of which):

(a)  demonstrates        CRF        Receptor         Antagonist         activity
     ****************************** ****************; and






(b)  demonstrates   CRF   Receptor   Antagonist   activity   at  a   dosage   of
     ***************************************************************************
     **************************************************************************,
     provided that at the request of  Neurocrine,  such activity is confirmed in
     the ******** by repeating the experiment; and

(c)  is within the scope of the Back-up Program Patents; and

(d)  is  discovered,  identified,  synthesized,  developed  or acquired by or on
     behalf of  Neurocrine  or Janssen  within the scope and during the  Back-up
     Program Term and is  recognized  by either Party to meet the  conditions of
     (a)  and (b)  hereof,  prior  to the  first  anniversary  of the end of the
     Back-up Program Term.

1. 3 "Back-up  Program" shall mean all work performed by the Parties or on their
behalf directed towards or in connection with the discovery,  identification and
synthesis of Back-up PCCs during the Back-up Program Term, but shall not include
work  performed  by Janssen on the PCCs of the  Original  Agreement  without the
direct cooperation or assistance of Neurocrine.

1. 4     "Back-up  Program  Patents"  shall  mean  the  Patents ****************
************   which  consist  of **********************************************
*****************   ******************  and  the  Neurocrine  Back-up Patents.

1.5 "Back-up  Program Term" shall mean the term  beginning on April 15, 1999 and
ending  February 15, 2001 or such earlier date as Janssen  shall  terminate  the
Back-up Program in accordance with section 2a.13.

1.6 "Neurocrine Back-up Patents" shall mean *************************** filed by
Neurocrine,  excluding any genus thereof  outlicensed  to a Third Party with the
knowledge of Janssen.

1.7 "Preliminary  Back-up  Candidate" shall mean a PCC,  including  Back-up PCC,
that meets the following criteria:

(i)      demonstrates ************************* in Exhibit B; and
(ii)     demonstrates the ******************** in Exhibit B; and
(iii)    demonstrates no **************** as set forth in Exhibit B; and
(iv)     falls  within  the scope of the claims of a Program  Patent,  including
         Back-up  Program  Patent,  or is licensed to Janssen and  Neurocrine by
         DuPont Pharmaceuticals  Company under the executed Settlement Proposal,
         and on the basis of review of published applications appears to be free
         of published Patent claims of Third Parties.

1.8  "Settlement  Proposal"  shall mean the  settlement  proposal among Janssen,
Neurocrine    and   a   Third   Party    (DuPont    Pharmaceuticals    Company),
****************************.





                                        4

                                    ARTICLE 2
                        AMENDMENT OF CERTAIN DEFINITIONS.

2.1 The definition of Collaboration  Tangible Research Product is hereby revised
to read as set forth below: ---------------------------------------

         "Collaboration  Tangible  Research  Product"  means any  composition of
         matter or other tangible asset, including but not limited to compounds,
         natural  products or  fermentation  broths and/or  extracts or factions
         thereof,  immunoglobulin molecules,  including active fragments thereof
         and monoclonal antibodies, cells and cell lines, DNA and RNA molecules,
         plasmids, proteins, peptides,  receptors,  receptor fragments, research
         tools,  materials for use in screening  methods and techniques  made or
         synthesized  by either  Party in the course of the  Research or Back-up
         Program,  or acquired by  Neurocrine  in the course of the  Research or
         Back-up  Program  with  funds  provided  by  Janssen  under  2.5(c)  or
         2a.7(iii) as mutually agreed.

2.2 The  definition of  Non-Collaboration  Tangible  Research  Product is hereby
revised to read as set forth below:

         "Non-Collaboration  Tangible Research Product" means any composition of
         matter or other tangible asset, including but not limited to compounds,
         natural  products or  fermentation  broths and/or  extracts or factions
         thereof,  immunoglobulin molecules,  including active fragments thereof
         and monoclonal antibodies, cells and cell lines, DNA and RNA molecules,
         plasmids, proteins, peptides,  receptors,  receptor fragments, research
         tools,  materials for use in screening  methods and techniques  made or
         synthesized by either Party outside of the Research or Back-up  Program
         before,  during or after the Research Term and Back-up Program Term and
         actually  utilized by such Party in conducting  the Research or Back-up
         Program, respectively.

2.3 The definition of Primary  Collaboration  Compounds or PCC is hereby amended
so that subparagraphs (c)(i) and (c)(ii) shall read as set forth below:

(i)                        is  (A)   discovered,   identified,   synthesized  or
                           acquired  by or on behalf of  Neurocrine  or  Janssen
                           prior  to  the  end  of  the  Research  Term  and  is
                           recognized by either Party to meet the  conditions of
                           (a) and (b) hereof, prior to the first anniversary of
                           the end of the Research Term or (B) is a Back-up PCC;
                           or
(ii)                       is (A) first discovered,  identified,  synthesized or
                           acquired by or on behalf of Janssen during the period
                           beginning  with  the  end of the  Research  Term  and
                           ending on the Amendment Effective Date and recognized
                           by Janssen to meet the  condition of (b) hereof prior
                           to the third  anniversary  of the end of the Research
                           Term,   or   (B)   first   discovered,    identified,
                           synthesized  or  developed  by  Janssen or by a Third
                           Party  directly  or  indirectly  on behalf of Janssen
                           during  the  period   beginning   on  the   Amendment
                           Effective Date and ending on the third anniversary of
                           the end of the Research Term and





                           recognized  by Janssen to meet the  condition  of (b)
                           hereof   during   such   period  if  the   discovery,
                           identification,  synthesis or development (whether by
                           Janssen or a Third Party) would, but for any licenses
                           granted  hereunder  or  pursuant  to  the  Settlement
                           Proposal, infringe any Neurocrine Patent; or

2.4 The  definition  of Program  Patents is hereby  amended to read as set forth
below:

         "Program  Patents" shall mean on a genus by genus basis, the genuses in
         any Patent (or pending  application  for a Patent) the subject of which
         is an invention  that (i) was conceived  (in a writing  provided to the
         other  Party) or reduced to  practice by Janssen or  Neurocrine  in the
         course of the  Research  or within the scope and during the term of the
         Back-up  Program and (ii) that comprises a PCC or SCC or a formulation,
         method of use or method of manufacture thereof.


                                    ARTICLE 3
                                OTHER AMENDMENTS

3.1  Amendment  of Paragraph  9.1.  Paragraph  9.1 of the Original  Agreement is
hereby amended so that the second sentence shall read as set forth below:

         Title to all  other  Patents  claiming  inventions  made  solely  by an
         employee of a Party in the course of performing Research or the Back-up
         Program shall be owned by such Party.

3.2  Amendment  of Paragraph  9.2.  Paragraph  9.2 of the Original  Agreement is
hereby amended so that the first sentence shall read as set forth below:

         Each  Party  shall  provide  to  the  other  any  invention  disclosure
         submitted in the normal course and  disclosing an invention  arising in
         the course of the Research or Back-up Program.

3.3      Amendment of Paragraph 10.3.  Paragraph 10.3 of the Original Agreement
is hereby amended to read as set forth below:

         10.3  Exclusivity/  Non-Competition.   During  the  Research  Term  and
         thereafter  until the Amendment  Effective Date,  Neurocrine  shall not
         conduct, have conducted or fund any research, development,  regulatory,
         manufacturing or commercialization  activity directed to the discovery,
         development or commercialization of CRF Antagonists for use in anxiety,
         depression  or  drug  abuse  except  as  permitted   pursuant  to  this
         Agreement.

3.4 Amendment of Paragraph  11.6.  The first  sentence of Paragraph  11.6 of the
Original Agreement is hereby revised to read as set forth below:

                  11.6 Termination for  Convenience.  Janssen may terminate this
         Agreement  for any  reason  without  cause  at any  time  with  further
         obligations  of payment on the part of Janssen being limited to amounts
         expected by Neurocrine under Paragraph 2.5 (including





         without  limitation  2.5(b)),  Paragraph 6.1 above and paragraph  2a.7,
         which  Neurocrine  would have  received if the  Agreement  had not been
         terminated under this Paragraph 11.6.

3.5 Amendment of Paragraph  15.8.  Paragraph  15.8 of the Original  Agreement is
hereby amended to read as set forth below.
                          ----------------------------


         15.8 Notices.  All notices  hereunder  shall be in writing and shall be
         deemed  given if  delivered  personally  or by  facsimile  transmission
         (receipt  verified),  telexed,  mailed by registered or certified  mail
         (return receipt requested), postage prepaid, or sent by express courier
         service,  to the  Parties at the  following  address  (or at such other
         address for a party as shall be  specified  by like  notice;  provided,
         that  notices  of a change  of  address  shall be  effective  only upon
         receipt thereof.

         If to Neurocrine,

           addressed to: Neurocrine Biosciences, Inc.
                         10555 Science Center Drive
                         San Diego, CA 92121
                         Attention: President & CEO
                         Telephone:  858-658-7600
                         Telecopy: 858-658-7605

       If to Janssen,

         addressed to:   Janssen Pharmaceutica,N.V.
                         Turnhoutseweg 30
                         2340 Beerse, Belgium
                         Attention: President, JRF
                         Telephone: (32 + 14) 60-21-11
                         Telecopy: (32 + 14) 60-28-41


         With a copy to:            Office of General Counsel
                                    Johnson & Johnson
                                    One Johnson & Johnson Plaza
                                    New Brunswick, NJ 08933

         Each of the Parties  consent to the personal  jurisdiction  of the U.S.
         Federal  Courts and agree to accept any legal process  served upon such
         Party at the addresses specified above for such Party.


                                                     ARTICLE 4
                                           ADDITION OF NEW ARTICLE II A

The Original  Agreement is hereby  amended by the addition of the  following new
article covering the terms and conditions under which the parties have agreed to
conduct the Back-up Program.






                                       13
                     [***] CONFIDENTIAL TREATMENT REQUESTED

                                  ARTICLE II A
                                 BACK-UP PROGRAM

         2a.1  Back-up  Program.  Janssen  and  Neurocrine  agree to  conduct  a
         collaborative  Back-up Program under the terms and conditions set forth
         in this Article II A.

                  (i) Scope. The scope of the Back-up Program will be limited to
                  identification,  characterization and pre-clinical development
                  of CRF  Antagonist  compounds  within the scope of the Back-up
                  Program Patents.  The Parties acknowledge that a number of CRF
                  Antagonist  Compounds  identified in the scope of the Research
                  have been designated  PCCs. It is anticipated that the Back-up
                  Program  will  focus on the  discovery  of new PCCs but to the
                  extent the JRC elects to conduct further  characterization and
                  development  of PCCs  identified in the course of the Research
                  as part  of the  Back-up  Program,  the  characterization  and
                  development of such PCCs shall be subject to the terms of this
                  Article II A.

                  (ii)    Goal. It is the goal of the Back-up Program to********
                  *************************************************************
                  **************************************************************
                  ********************************.
                  The  Parties  will in good faith use  commercially  reasonable
                  efforts  to  meet  the  goals  of  the  Back-up  Program.  For
                  clarification,  there is no  obligation on the part of Janssen
                  to file an IND or any equivalent thereof on any PCC, including
                  Back-up PCC, imposed by the operation of this Amendment except
                  as provided in 2a.8(ii).

         2a.2     The JRC.

                  (i) Formation.  Janssen and Neurocrine  will establish a Joint
                  Research and Development Committee ("JRC") to oversee,  review
                  and  co-ordinate  the Back-up  Program and the  implementation
                  thereof.  The JRC will  consist of at least  three (3) members
                  from  each  of  Janssen  and  Neurocrine   (with  Janssen  and
                  Neurocrine having equal representation).

                  (ii) Decisions. Each Party shall have one consolidated vote on
                  any issue and decisions of the JRC shall be by unanimous vote.
                  If  the  JRC  fails  to  resolve  any  matter  before  it  for
                  consideration,  the matter  shall be resolved  pursuant to the
                  dispute resolution provisions of Paragraph 13.1.

                  (iii) FTE use. The JRC will use reasonable efforts to allocate
                  work  under the Plan to supply  Neurocrine  with  Neurocrine's
                  expected  utilization  rate of  approximately  ******/calendar
                  quarter.  The JRC may provide  that FTE  utilization  be moved
                  from one quarter to another where such is in the best interest
                  of the Plan and convenient to Neurocrine.

                  (iv)  Subcommittees.  From time to time the JRC may  establish
                  subcommittees  to oversee  particular  projects or  activities
                  (such as separate committees to manage





                  the  research  phase  and  pre-clinical  phase of the  Back-up
                  Program) and such  committees  will be  constituted as the JRC
                  agrees.

                  (v)  Meetings.  The JRC will  meet  regularly  according  to a
                  mutually agreed schedule.

         2a.3     Research Plan.

(i)                 Agreement on Research  Plan.  Promptly  after the  Amendment
                    Effective Date, the Parties shall meet and mutually agree on
                    a plan for the conduct of the Back-up  Program (the "Plan").
                    The Plan will  outline the Back-up  Program  objectives  and
                    timeline and describe the activities to be conducted by each
                    Party. The JRC shall review the Plan on an ongoing basis and
                    approve  changes thereto as the JRC deems  appropriate.  The
                    Plan  shall  be  consistent  with  this  paragraph  2a.3 and
                    consistent with each Party's available resources. An initial
                    Plan is outlined in Exhibit B.

(ii)                Efforts.  The Plan will include general  responsibilities of
                    Neurocrine and Janssen FTEs devoted to the Back-up  Program.
                    Neurocrine    will    commit   to    devote    approximately
                    ***************  FTEs in total to the conduct of the Back-up
                    Program.  Janssen  will  play an  active  role  in both  the
                    research phase and pre-clinical phase of the Back-up Program
                    and commit resources accordingly.

(iii) Responsibilities.

(A)                          Neurocrine. The Parties have agreed that Neurocrine
                             will be responsible for the initial identification,
                             synthesis  and  pharmacological  and  toxicological
                             profiling of PCCs,  including  Back-up PCCs, during
                             the Back-up  Program.  This will include  medicinal
                             chemistry,   synthesis   scale  up,  in  vitro  CRF
                             receptor studies, in vivo  pharmacological  studies
                             related to depression, anxiety and substance abuse,
                             pharmacokinetics,     non-GLP     toxicology    and
                             teratogenicity screening.

(B)                          Janssen.  The Parties have agreed that Janssen will
                             be  responsible  for  testing  of  PCCs,  including
                             Back-up PCCs,  which are suitably  scaled up in the
                             ***************************************************
                             and for GLP toxicology.  Subject to the obligations
                             imposed by sub-Paragraph 2a.1(ii) and regardless of
                             2a.2(ii),  Janssen  shall  have  final say of which
                             compounds are scaled up for further  testing at any
                             point where scale up from the initial  synthesis is
                             necessary.  Any decision on which Janssen has final
                             say will be  consistent  with the  objective of the
                             Plan and with timelines contained therein.

         2a.4 Identification of Preliminary Back-up Candidate. The determination
         of whether a Preliminary  Back-up Candidate has been identified will be
         based upon the good faith results of the above mentioned animal models.
         In the case of the *****************





         ****************************************, the model may be run a second
         time and the average result will be  determinative.  In the case of the
         ********************   **************,   the  first   results  will  be
         determinative.

         2a.5  Collaboration  Tangible  Research  Products.  During the  Back-up
         Program Term each Party shall use reasonable  efforts to make available
         to the other,  Collaboration  Tangible  Materials  to the  extent  such
         transfer  shall be  reasonably  necessary  for a party to conduct their
         responsibilities under the Plan.

         2a.6 Reports.  Janssen and Neurocrine  will use  reasonable  efforts to
         make available and disclose to one another Information known by Janssen
         or Neurocrine on the Amendment  Effective Date that directly relates to
         the scope of the  Back-up  Program.  During the  Back-up  Program  Term
         Janssen and Neurocrine  will use reasonable  efforts to disclose to one
         another  Information  regarding  compounds  synthesized  or discovered,
         initial  leads,  activities  of leads,  derivatives,  and results of in
         vitro and in vivo  studies  arising in the course of the conduct of the
         Back-up Program.  Notwithstanding the foregoing, the Parties agree that
         Information  disclosed during the course of the Back-up Program will be
         limited to  Information  within the scope of the  Back-up  Program  the
         disclosure of which is reasonably  necessary for the Parties to conduct
         the Back-up  Program in accordance  with the Plan.  Consistent with the
         above,  each  Party  will  provide  the  other  with  raw data for work
         conducted in the course of the Back-up Program to the extent reasonably
         requested by the other Party.

         2a.7     Funding.

(i)               Prior Efforts. In consideration of research conducted and data
                  and information generated prior to the Effective Date, Janssen
                  will              pay              to               Neurocrine
                  ****************************************  within  thirty  (30)
                  days of the Amendment Effective Date.

                  (ii)  FTEs.  Janssen  will  reimburse   Neurocrine  for  costs
                  associated   with  the  conduct  of  the  Back-up  Program  by
                  Neurocrine    personnel    by    providing    funding    equal
                  **************************************************         per
                  calendar  quarter  for the Back-up  Program  Term or until the
                  total                   sum                    ***************
                  ****************************************************  is paid.
                  Such  funding  shall  be  provided  in  advance  in  quarterly
                  installments.  The  payments  for the first and last  quarters
                  shall be prorated to reflect the April 15, 1999 effective date
                  for the Back-up Program Term with the first such payment being
                  due and payable  within  thirty (30) days after the  Amendment
                  Effective  Date and the first  payment  shall include past due
                  amounts for calendar  1999 as well as the advance  payment for
                  the fourth quarter of 1999.

                  (iii)  Outside  Costs.  Janssen  will be  responsible  for all
                  outside and third party costs  associated with Back-up Program
                  activities approved by the JRC in the Plan including the costs
                  associated  with third party  contractors  retained to perform
                  tasks  approved by the JRC. In addition,  Janssen may elect to
                  have third party





                  contractors  reasonably  acceptable to Neurocrine perform some
                  of Janssen's  obligations under the Plan to the extent Janssen
                  is unable to perform the task  internally  within the approved
                  timeline  or  when  Janssen  otherwise  deems  it  appropriate
                  consistent with the goals of the Back-up  Program.  Similarly,
                  Neurocrine  may  elect  to use  third  party  contractors  for
                  certain toxicology,  manufacturing and other tasks approved by
                  the JRC.  Janssen will be responsible for all such third party
                  costs. Regardless of 2a.2(ii), Janssen shall have final say as
                  to all outside and third Party Costs  associated  with Back-up
                  Program activities,  including the costs associated with Third
                  Party  contractors  retained to perform tasks  approved by the
                  JRC.  Any  decision  on which  Janssen  has  final say will be
                  consistent  with the objectives of the Plan and with timelines
                  contained therein.

                  (iv) Records.  Neurocrine will maintain  complete and accurate
                  records relevant to the expenditure of Back-up Program funding
                  hereunder.  Such  records  shall  be  open  during  reasonable
                  business  hours for a period of three (3) years  from the date
                  of creation of such  records for the sole  purpose of allowing
                  Janssen to verify payments hereunder.

         2a.8     Milestones

                  (i)  Payments.  Within  thirty (30) days  following  the first
                  occurrence  of the events set forth below,  Janssen shall make
                  the following one-time milestone payments to Neurocrine:

                  Event Payment
                  Identification of Preliminary Back-up Candidate,
                  which Preliminary Back-up Candidate ******
                  *******************************************
                  ***********************************

                  Filing and  acceptance for review of an IND or equivalent in a
                  country of the European Union of a PCC, including Back-up PCC,
                  discovered, identified or synthesized or developed
                  in the Back-up Program *************

                  In the event the event that the  milestone on  acceptance  for
                  review   of  an  IND  is   paid,   then  the   milestone   for
                  identification of a Preliminary Back-up Candidate will be paid
                  where  it  was  previously  unpaid.  The  milestones  of  this
                  Paragraph will be paid in total only once.  Milestone payments
                  based on further post IND  development  of a PCC  developed in
                  the scope of the Back-up Program will be subject to any unpaid
                  milestones under Paragraph 6.3.

                  (ii) Diligence. In the event that Janssen has not incurred the
                  obligation       to      pay      the       milestone      for
                  *********************************************,  then  upon the
                  later       of      six       (6)       months       following
                  ********************************** or





nine              (9)  months   following   ************************************
                  **************************************************************
                  **************************************************************
                  agrees  to  either  (A) pay such  milestone  *****************
                  ******************************,   or  (B)  on  a  compound  by
                  compound    basis    *****************************************
                  **************************************************************
                  **************************************************************
                  **************************************************************
                  ***********************************************.
                  The return of rights  under this  sub-Paragraph  will  include
                  rights to all data and  information and be free of any royalty
                  obligation to Janssen.

                  (iii)   In   the    event    that    the    milestone    for
                  **************************************************************
                  **************************************** and the Milestone For
                  **************************************************************
                  *************************************************************
                  *************************************************************,
                  then Janssen agrees to pay such  milestone for  identification
                  of a Back-up  Preliminary  Candidate at the time the milestone
                  is paid pursuant to 2a.8(i) or 2a.8(ii).

         2a.9 Royalties.  Janssen will pay to Neurocrine  Royalties on Net Sales
         of PCCs  developed in the scope of the Back-up  Program as set forth in
         Article VI.

         2a.10    Clinical Development and Commercialization.

(i)                 Clinical Development. Clinical development of PCCs developed
                    in the course of the Back-up  Program  will be  conducted in
                    accordance with Article III.

(ii)                Commercialization.  Commercialization  of PCCs  developed in
                    the  course of the  Back-up  Program  will be  conducted  in
                    accordance with Article IV.

(iii)               Manufacture.   Janssen   shall   be   responsible   for  the
                    manufacture  of PCCs  developed  in the scope of the Back-up
                    Program consistent with Article VII.

(iv)                Indemnification.  For  the  purposes  of  Article  XII,  the
                    conduct  of  the  Back-up  Program  shall  be  considered  a
                    Research and Development activity.

         2a.11    Licenses and Patents.

(i)                 Back-up  Program.  Janssen  hereby  grants to  Neurocrine  a
                    non-exclusive  license under the Janssen Patents and Program
                    Patents  as shall be  reasonably  necessary  or  useful  for
                    Neurocrine to conduct the Back-up Program. Neurocrine hereby
                    grants  to  Janssen  a   non-exclusive   license  under  the
                    Neurocrine  Patents  (including  Neurocrine Back-up Patents)
                    and  Program  Patents as shall be  reasonably  necessary  or
                    useful for Janssen to conduct the Back-up Program.
(ii)




                  Janssen.  Janssen will receive  rights and assume  obligations
                    consistent  with Article IX for any back-up  Program Patents
                    that are  determined  during  the  Back-up  Program  Term to
                    actually  contain  a PCC  to  the  extent  Janssen  did  not
                    previously  have  such  rights  and  obligations.  Upon  the
                    determination  that all or a portion of a Neurocrine Back-up
                    Patent  is  a  Program   Patent,   Janssen  will   reimburse
                    Neurocrine for past fees and expenses  incurred with respect
                    to all or part of such Patent,  as the case may be, prior to
                    such   determination.   Thereafter,   Janssen   will  assume
                    responsibility  for  such  Program  Patent  consistent  with
                    Article IX.

         2a.12   Exclusivity/   Non-Competition.   Janssen   acknowledges   that
         Neurocrine has informed  Janssen that during the period between the end
         of the Research Term and the Amendment  Effective Date,  Neurocrine has
         conducted an internal  research  program  directed to the discovery and
         characterization  of CRF Antagonist  compounds which do not fall within
         the scope of the  Program  Patents  ("Neurocrine  Compounds")  with the
         intention  of   developing   these   compounds  for  stroke  and  other
         indications that would not be categorized as anxiety, depression and/or
         drug abuse  within the time  periods  dictated by  Paragraph  10.3 and,
         following the expiration of the limitations  imposed by Paragraph 10.3,
         expanding the development of these compounds to anxiety, depression and
         drug  abuse  should  the   compounds   demonstrate   activity  in  such
         indications.  Neurocrine  has also informed  Janssen that  Neurocrine's
         willingness to conduct the Back-up  Program is conditioned on Janssen's
         recognition  of  Neurocrine's  continued  right to conduct  independent
         research and development of CRF Antagonist compounds.  It is understood
         that     **************************************************************
         **************************     entitles     the    Parties    to    use
         ********************  *******************  for any  purpose  subject to
         obligations of  confidentiality in Article VIII. This would include the
         use  of   ******************************  in  the  development  of  the
         ********************.

         2a.13    Termination.

(i)               Convenience.  In the event  Janssen  shall elect to  terminate
                  this  Agreement  under  Paragraph  11.6,  Janssen shall pay to
                  Neurocrine  all  amounts  that would have been  payable  under
                  Paragraphs 2a.7(ii) (up to ********************) and reimburse
                  Neurocrine  for  all  noncancelable  obligations  incurred  by
                  Neurocrine for JRC approved activities.

(ii) Breach.  Notwithstanding  the  provisions  of paragraph  11.2, in the event
either Party shall default in  ---------------  the  performance of any material
obligation  set forth in this  Article II A, the sole  remedy of the other Party
shall be termination of the Back-up  Program.  In the event the Back-up  Program
shall be  terminated  by reason of a default by  Janssen,  Janssen  shall pay to
Neurocrine all amounts that would have been payable under paragraph 2a.7(ii) and
(iii),  grant to  Neurocrine an exclusive  license under the Program  Patents to
make,  use and sell Back-up PCCs which are  Preliminary  Back-up  Candidates and
reimburse  Neurocrine for all noncancelable  obligations  incurred by Neurocrine
for JRC approved activities. In the event the (iii)




                  Back-up  Program shall be terminated by reason of a default by
                  Neurocrine,  Neurocrine  will  return to Janssen  the  initial
                  payment and any milestone  payments made by Janssen  hereunder
                  and any Neurocrine  Back-up Patent and Back-up  Program Patent
                  that  contains  a  Preliminary   Back-up   Candidate  will  be
                  considered a Program  Patent which  contains in each  chemical
                  genus  thereof at least one member  which is a PCC meeting the
                  requirements of Paragraph 1.38 (c)(i).

                  (iii)  Early  Termination.  Janssen  shall  have the  right to
                  terminate  the  Back-up  Program  as   ****************   upon
                  delivering  notice of its intention to do so by *************.
                  Upon such termination,  Janssen will reimburse  Neurocrine for
                  noncancelable  obligations  incurred  by  Neurocrine  for  JRC
                  approved  activities  and  thereafter  shall  have no  further
                  obligation  to fund the  conduct  of the  Back-up  Program  by
                  Neurocrine.   Janssen  will  retain  all  rights,   patent  or
                  otherwise, to PCCs which are such by the terms of the Original
                  Agreement except that any development of such a PCC by Janssen
                  which was discovered,  identified, synthesized or developed in
                  the Back-up Program will be subject to the milestone  payments
                  herein. Upon such termination,  Neurocrine will retain all its
                  rights, patent or otherwise, to any compound which, except for
                  the terms of this Amendment would not be a PCC. The definition
                  of  Program  Patent  would  return  to  that  of the  Original
                  Agreement.    Neurocrine's    retained   rights   under   this
                  sub-Paragraph  will  be  free  of any  royalty  obligation  to
                  Janssen and include all rights to data.


                                    ARTICLE V
                                  MISCELLANEOUS

5.1 Assignment. Either Party may assign this Amendment or its ownership interest
in jointly owned Program Patents:  (i) to a party that succeeds to substantially
all of the  business  or assets of such  Party by reason of a merger or  similar
reorganization  or the sale of substantially  all of its business or assets,  or
(ii) otherwise with the prior written consent of the other Party. This Amendment
shall be binding upon and inure to the benefit of the  successors  and permitted
assigns of the Parties.  Any  assignment  not in accordance  with this Amendment
shall be void.

5.2 Force Majeure. Neither Party shall lose any rights hereunder or be liable to
the other  Party for damages or losses on account of failure of  performance  by
the  defaulting  Party if the failure is occasioned by government  action,  war,
fire,  explosion,  flood,  strike,  lockout,  embargo,  act of God, or any other
similar  cause beyond the control of the  defaulting  Party,  provided  that the
Party  claiming  force  majeure has exerted all  reasonable  efforts to avoid or
remedy such force majeure; provided,  however, that in no event shall a Party be
required to settle any labor dispute or disturbance.

5.3. Further Actions. Each Party agrees to execute, acknowledge and deliver such
further  instruments,  and to do all such other  acts,  as may be  necessary  or
appropriate in order to carry out the purposes and intent of this Amendment






5.4 Waiver.  Except as specifically provided for herein, the waiver from time to
time by  either  of the  Parties  of any of their  rights  or their  failure  to
exercise any remedy shall not operate or be construed as a continuing  waiver of
same or of any  other  of such  Party's  rights  or  remedies  provided  in this
Amendment.

5.5  Severability.  If any term,  covenant or condition of this Amendment or the
application  thereof to any Party or circumstance  shall, to any extent, be held
to be invalid or unenforceable, then (i) the remainder of this Amendment, or the
application  of such term,  covenant or  condition  to Parties or  circumstances
other than those as to which it is held invalid or  unenforceable,  shall not be
affected thereby and each term, covenant or condition of this Amendment shall be
valid and be enforced  to the  fullest  extent  permitted  by law;  and (ii) the
Parties  hereto  covenant and agree to  renegotiate  any such term,  covenant or
applicable  thereof in good faith in order to  provide a  reasonably  acceptable
alternative  to the  term,  covenant  or  condition  of  this  Amendment  or the
application thereof that is invalid or unenforceable, it being the intent of the
Parties that the basic purposes of this Agreement are to be effectuated.

5.6  Counterparts.  This Amendment may be executed in two or more  counterparts,
each of which  shall be  deemed an  original,  but all of which  together  shall
constitute one and the same instrument.

5.7 Entire Agreement. The Original Agreement as amended hereby, the accompanying
Stock  Purchase  Agreement   ***************************************************
******  set  forth  all  the  covenants,   promises,   agreements,   warranties,
representations,  conditions and  understandings  between the Parties hereto and
supersede and  terminate  all prior  agreements  and  understanding  between the
Parties.   There   are   no   covenants,   promises,   agreements,   warranties,
representations,  conditions or understandings,  either oral or written, between
the  Parties  other  than  as  set  forth  herein  and  therein.  No  subsequent
alteration,  amendment,  change or addition to this  Amendment  shall be binding
upon the Parties  hereto unless  reduced to writing and signed by the respective
authorized officers of the Parties.

  5.8  Relationship of Parties.  Nothing herein shall be construed to create any
  relationship  of employer and employee,  agent and  principal,  partnership or
  joint venture  between the Parties.  Each Party is an independent  contractor.
  Neither Party shall assume, either directly or indirectly, any liability of or
  for the  other  Party.  Neither  Party  shall  have the  authority  to bind or
  obligate the other Party and neither  Party shall  represent  that it has such
  authority.







                                       14

IN WITNESS  WHEREOF,  the Parties have  executed  this  Amendment as of the date
first written above.

NEUROCRINE BIOSCIENCES, INC.


/s/Gary Lyons
By: Gary Lyons
President & CEO



JANSSEN PHARMACEUTICA, N.V.

/s/Dr. Alan Dunton
By: Dr. Alan Dunton
President





                     [***] CONFIDENTIAL TREATMENT REQUESTED
                                    EXHIBIT A

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                                    EXHIBIT B


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