<PAGE>

EXHIBIT 10.53



               INSTRUMENT, ASSAY DEVELOPMENT AND LICENSE AGREEMENT

                                     BETWEEN

                     GLAXO RESEARCH AND DEVELOPMENT LIMITED

                                       AND

                               GLAXO GROUP LIMITED

                                       AND

                         AURORA BIOSCIENCES CORPORATION


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This Agreement is made by and between GLAXO RESEARCH AND DEVELOPMENT LIMITED AND
GLAXO GROUP LIMITED both with their principal offices at Glaxo Wellcome House,
Berkeley Avenue, Greenford, Middlesex UB6 ONN, United Kingdom, (together with
any Affiliate company, "GW") and AURORA BIOSCIENCES CORPORATION ("Aurora"), a
Delaware corporation with principal offices at 11010 Torreyana Road, San Diego,
California 92121, U.S.A.

                                    RECITALS

WHEREAS, GW and Aurora wish to enter into an agreement involving the purchase by
GW of a Voltage Ion Probe Reader (VIPR) from Aurora, collaborative research to
develop ***, and licenses of rights from Aurora to GW to use the VIPR as well as
Aurora's Voltage Sensor Probes (VSPs) and the *** to practice the technologies
*** as set forth herein.

Now, therefore, in consideration of the foregoing and the covenants and premises
contained herein the parties agree as follows:

1.       DEFINITIONS

         1.1      "ACHIEVEMENT OF PROOF OF CONCEPT" means the point at which the
                  initial human efficacy trial is successfully completed and a
                  compound approved for further development by GW, such decision
                  usually being agreed to at a meeting of the GW Therapeutic
                  Management Team, or its functional equivalent.

         1.2      "AFFILIATE" means (1) any corporation or other entity directly
                  or indirectly owning or controlling, at least *** of the stock
                  entitled to vote for election of directors with a party to
                  this Agreement or otherwise having the power to direct the
                  management and policies of a party to this Agreement, (2) any
                  corporation or other entity of which a party to this Agreement
                  directly or indirectly owns or controls at *** of the stock
                  entitled to vote for election of directors or otherwise has
                  the power to direct the management and policies, (3) any
                  corporate or other entity directly or indirectly under common
                  control with a party to this Agreement; provided, however,
                  that in the circumstance where the country of incorporation of
                  such owned or controlled corporation or other entity requires
                  the maximum ownership by a foreign entity be less ***, the
                  percentage of ownership required to make such an entity an
                  affiliate must be equal to the maximum percentage of ownership
                  permitted by such country provided the operational control is
                  held by a party to this Agreement.


         1.3      "ASSAY" means a ***.



         1.4      "ASSAY TRANSFER DATE" means the date that GW receives delivery
                  ***, *** Assay *** Collaborative Research Plan, this date ***
                  of the Assay by the Steering Committee.

         1.5      "AURORA FACTORY CERTIFIED ENGINEERS" means engineers provided
                  by Aurora to service


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                  the VIPR ***.

         1.6      "AURORA PATENTS" means *** and *** set forth in Exhibit A and
                  *** issuing therefrom.




         1.7      "AURORA TECHNOLOGY" means Materials and Know-How owned or
                  Controlled by Aurora on or before the Effective Date and
                  necessary for the Collaborative Research Program.

         1.8      "COLLABORATIVE RESEARCH PROGRAM" means the collaboration
                  between Aurora and GW as set forth in Exhibit B for the
                  development ***.

         1.9      "COLLABORATIVE RESEARCH PLAN" means that project plan attached
                  as Exhibit B hereto, which may be amended from time to time,
                  upon written mutual agreement of Aurora and GW.

         1.10     "CONFIDENTIAL INFORMATION" means all information, data, and
                  documentation received by either party from the other party
                  pursuant to this Agreement and if in writing, designated as
                  confidential at the time of disclosure, subject to the
                  exceptions set forth in Section 9.1.

         1.11     "CONTROL" OR "CONTROLLED" means, in the context of
                  intellectual property, possession by a party of the ability to
                  grant a license or sublicense in accordance with the terms of
                  this Agreement, and without violating the terms of any
                  agreement by such party with any Third Party.

         1.12     "EFFECTIVE DATE" means the latest date on which the Agreement
                  is executed by a party hereto.


         1.13     "GW COMPOUNDS" means *** compounds and *** that GW shall
                  provide to Aurora in a format *** and that shall be screened
                  by Aurora in accordance with Section ***.




         1.14     "GW MATERIALS" means Materials provided by GW to Aurora in
                  furtherance of the Collaborative Research Program.

         1.15     "GW TECHNOLOGY" means GW Materials and Know-How owned or
                  Controlled by GW on or before the Effective Date and necessary
                  for the Collaborative Research Program.

         1.16     "INVENTION" means ***.

         1.17     "KNOW-HOW" means information and data owned or Controlled by a
                  party hereto, which is existing as of the Effective Date or
                  which a party develops or acquires as part of the
                  Collaborative Research Program which is not generally known to
                  the public, comprising: designs, concepts, algorithms,
                  formulae, techniques, practices, processes,


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                  methods, knowledge, skill, experience, expertise and technical
                  information.

         1.18     "MATERIALS" means any reagents, cell lines, promoters,
                  enhancers, vectors, plasmids, genes, proteins and fragments
                  thereof, peptides, antigens, antibodies, agonists,
                  antagonists, inhibitors and chemicals.

         1.19     "PATENT RIGHTS" means all U.S. or foreign (including regional
                  authorities such as the European Patent Office) regular or
                  provisional patent applications, including any continuation,
                  continuation-in-part, or division thereof or any substitute
                  application therefor or equivalent thereof, and any patent
                  issuing thereon, including any reissue, reexamination or
                  extension thereof and any confirmation patent or registration
                  patent or patent of additions based on any such patent,
                  containing one or more claims to an Invention (and in the case
                  of an issued patent, containing one or more claims), and for
                  which a party hereto owns or Controls, individually or
                  jointly, any title thereto or rights thereunder.

         1.20     "PRE-CLINICAL CANDIDATE SELECTION" means the point at which
                  lead optimization is concluded and a candidate for further
                  development is selected, ***.



         1.21     "PRODUCT LAUNCH" means the first commercial sale of a product.

         1.22     "***" means *** and ***.

         1.23     "TECHNOLOGY" means Materials and Know-How.

         1.24     "THIRD PARTY" means any person or entity other than Aurora and
                  GW or its Affiliates.

         1.25     "TRACKING RECORD" means tracking records referred to in
                  Section 5.8.

         1.26     "VIPR" means Aurora's voltage-ion probe reader as described in
                  Attachment 1 ***.


         1.27     "VOLTAGE SENSOR PROBES" OR "VSPS" means *** the Aurora
                  Patents.




2.       EQUIPMENT PURCHASE


         2.1.     SHIPMENT. Subject to GW's payments in Section 5, Aurora will
                  ship to GW's *** on or before ***. Aurora will *** support and
                  technical specifications *** the *** GW's ***. GW will also be
                  provided *** described in Section 2. *** updates regarding the
                  ***, produced by or on behalf of Aurora.


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         2.2.     INSTALLATION ***. Subject to GW's payments in Section 5,
                  Aurora will install *** site within *** days of the Assay
                  Transfer Date. Reasonable travel and expenses of Aurora
                  personnel directly related to the installation and validation
                  shall be billed separately at GW's expense.


         2.3.     TRAINING. Subject to GW's payments in Section 5, Aurora will
                  provide a comprehensive consecutive *** training session on
                  the operation of the VIPR for up to *** GW scientists *** to
                  be scheduled approximately at the time of the installation
                  ***. Travel and related expenses for Aurora personnel will be
                  paid by GW. In addition, *** GW engineers will be trained at
                  Aurora and certified by Aurora for routine servicing of ***
                  Dollars ($***), such training to take place prior to the
                  delivery ***.



         2.4.     WARRANTY. Subject to GW's payments in Section 5, *** with a
                  *** warranty, entitling GW to *** years of *** support, a
                  total of *** (*** annually) by an Aurora Factory Certified
                  Engineer provided by Aurora*** parts, which are *** and ***
                  service invoice after any *** repair. Travel and related
                  expenses for Aurora personnel for ***. Travel and related
                  expenses for service visits other than preventative
                  maintenance visits shall be paid by GW. No one other than an
                  Aurora Factory Certified Engineer is authorized to service
                  ***, and any tampering with or modification of the instrument
                  by any other party will nullify the warranty ***, ***, ***
                  personnel *** in any month, *** additional *** cost, ***
                  months of *** and *** to be confirmed in writing by Aurora.
                  *** as *** support *** day of request *** for ***, if needed,
                  within *** of request.








3.       COLLABORATIVE RESEARCH


         3.1.     ASSAY DEVELOPMENT AT AURORA. Aurora will use *** to develop,
                  in collaboration with GW, *** in a *** of the Effective Date
                  (the "Collaborative Research Program"). Aurora will then
                  transfer *** with *** and an *** within *** of *** Committee.
                  Criteria *** defined in the Collaborative Research Plan.





                  3.1.1.   *** DELIVERY OF ***. If Aurora *** to GW *** months
                           of the Effective Date, GW, *** either: (i) *** and
                           *** and *** and approval *** is


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                           contractually precluded from licensing to Third
                           Parties; or (ii)*** Sections *** and *** and *** .

                 3.1.2.    ***. In the event that all other *** the *** the ***
                           specified in Exhibit B, the parties ***, or ***
                           Aurora based upon ***, unless the ***, in which
                           case ***. In the event *** shall promptly ***
                           Aurora.

         3.2.     MATERIALS FROM GW. GW will provide pursuant to this Agreement
                  the GW Materials and GW Compounds, or a mutually agreed upon
                  subset thereof, to Aurora within *** days of the Effective
                  Date, and before ***, respectively. Aurora will not use GW
                  Materials or GW Compounds for any purpose other than those
                  described in this Agreement. *** GW.








         3.3.     SCREENING OF GW COMPOUNDS. Upon validation *** with the
                  Collaborative Research Plan and payment by GW according to
                  Section 5.5, Aurora shall undertake to screen the GW Compounds
                  ***. Such screening by Aurora shall be completed within *** of
                  *** and receipt of the GW Compounds. Upon completion of such
                  screening and written agreement of the parties, ***, as agreed
                  upon in the Collaborative Research Plan, GW shall pay Aurora
                  in accordance with Section 5.5 for performance of such
                  screening.




         3.4.     STEERING COMMITTEE. The Collaborative Research Program shall
                  be managed by a joint steering committee (the "Joint Steering
                  Committee") of a size and composition to be determined in good
                  faith by the parties and indicated in writing, with equal
                  representation from both GW and Aurora. Each member of the
                  Joint Steering Committee shall have ***. The Joint Steering
                  Committee shall meet on a schedule and in a venue or format
                  mutually agreed. Initial meetings shall by teleconference
                  every ***.



         3.5.     ***. During the period of the Collaborative Research Program,
                  ***so ***.


4.       LICENSES AND OPTION


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         4.1.     NON-EXCLUSIVE LICENSE. Aurora hereby grants to GW and its
                  Affiliates a *** license under the Aurora Patents and Aurora
                  Technology solely to *** Aurora or *** for *** and ***. GW
                  shall notify Aurora of any *** in writing. The license grant
                  of this Section 4.1 shall be effective until the date of the
                  *** anniversary of the ***. The license, at that point, may be
                  *** described in Section ***. The license grant of this
                  Section 4.1 may be ***, to allow GW to *** to be proposed by
                  GW *** other than in the event that Aurora is contractually
                  precluded from licensing to Third Parties, should GW ***,
                  during the time period such license grant is in effect, or
                  should Aurora *** GW *** of the Effective Date, in accordance
                  with Section ***.





         4.2.     *** LICENSE. Aurora hereby grants to GW *** license granted in
                  Section 4.1 above *** on an *** Dollars ($***) to be paid to
                  Aurora *** (the "***") and each subsequent anniversary of the
                  *** for up to ***. Such *** the date *** prior to the ***
                  anniversary of the *** or a later date taking into account any
                  ***. It is understood that the *** under Section ***.










         4.3.     RETAINED RIGHTS AND LIMITATIONS. The licenses under this
                  Section 4 are subject to GW's obligations described herein
                  including payments by GW as set forth in Section 5. For
                  clarity, the license rights granted to GW in this Section 4
                  specifically exclude the right 1) ***. Aurora retains the
                  right to work with other parties on the same or similar
                  targets, compounds, data and cell lines supplied by a Third
                  Party or independently developed by Aurora without the use of
                  GW Confidential Information, GW Compounds, or GW Materials.
                  Except as expressly licensed herein, GW *** or *** under the
                  Aurora Patents and Aurora Technology.





5.       PAYMENTS


         5.1.     EQUIPMENT PURCHASE. In consideration for the purchase of the
                  VIPR, GW shall pay to Aurora a total of *** Dollars ($***)
                  according to the following schedule of non-refundable,
                  non-creditable payments:


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                  5.1.1.   A *** Dollar ($***) pre-payment due upon the
                           Effective Date; and

                  5.1.2.   A *** Dollar ($***) payment due on ***.


                  Shipping will be prepaid and added FOB San Diego to the
                  invoice.

         5.2.     COLLABORATIVE RESEARCH. In consideration for the development
                  of ***, or in the event that GW *** Assay is ***, GW shall pay
                  to Aurora in accordance with the following schedule of
                  non-refundable, non-creditable payments:

                  5.2.1.   *** Dollars ($***) on the Effective Date; and
                  5.2.2.   *** Dollars ($***)*** Assay Transfer Date is *** ;
                           ***
                  5.2.3.   *** Dollars ($***)*** Assay Transfer Date is ***
                           Effective Date and ***; ***
                  5.2.4.   *** Dollars ($***)*** Assay *** months *** and *** GW
                           does *** Agreement.



         5.3.     LICENSE FEES. In consideration for the licenses granted in
                  Section 4.1, GW shall pay to Aurora a non-refundable,
                  non-creditable license fee of ***Dollars ($***), first due on
                  the Assay Transfer Date and then each anniversary of the Assay
                  Transfer Date for a total *** payments and *** Dollars ($***).
                  ***.



         5.4.     REAGENT SUPPLY. In consideration for the provision of the VSPs
                  by Aurora to GW, GW shall pay to Aurora *** Dollars ($***) for
                  *** of the VSPs. Such *** shall be delivered to GW on the ***.
                  GW's payment for such VSPs is due upon receipt. For subsequent
                  orders of VSPs from Aurora during the period from the Assay
                  Transfer Date to the *** anniversary of the Effective Date, GW
                  shall pay ***.





         5.5.     SCREENING PAYMENT. In consideration for the screening services
                  provided in Section 3.3, GW shall pay to Aurora, the amount
                  equal to *** Dollars ($***) for such agreed screening program.
                  Such payment is due within *** after the Assay Transfer Date.



         5.6.     WARRANTY PAYMENTS. In consideration for the warranty described
                  in Section 2.4, GW shall pay to Aurora (i) *** Dollars ($***)
                  on the first anniversary of the Assay Transfer Date ***; and
                  (ii) *** Dollars ($***) on the *** for the ***.



         5.7.     ***. In addition to other fees described in this Section 5, GW
                  shall also pay to Aurora ***, ***:


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<TABLE>
<CAPTION>
                           Event                               Milestone Payment
                           -----                               -----------------

<S>                                                                   <C>
                           ***                                         ***
</TABLE>





         5.8.     PAYMENT AND TRACKING MILESTONES. The milestones due under this
                  Section 5 shall be paid within *** days after the end of each
                  calendar quarter period in which such milestones are earned
                  and ***. The compounds and target tested using the Assay
                  developed under this Agreement will be recorded and stored by
                  GW using its customary means and in a computer searchable
                  database on a storage device. The information stored will
                  include the target, screen type, the concentration, structure
                  and activity of the compound tested, and date of testing.
                  Records of any hits, derivatives or any compound subject to
                  additional screening or evaluation will be stored by GW in a
                  computer searchable file or database that may or may not be
                  separate from other GW data not related to the Assay. GW shall
                  keep appropriate records of compounds discovered, identified
                  or profiled with the Assay subjected to ***. All the records
                  described in this Section are collectively referred to as
                  tracking records (the "Tracking Records"). GW *** by Aurora
                  and agreed to by GW, and *** GW, to inspect the Tracking
                  Records once per year upon reasonable prior written request by
                  Aurora for the sole purpose of determining the attainment of a
                  milestone under this Section 5. The Tracking Records shall be
                  securely retained *** for no less than *** years from ***.
                  Until all of the milestones have been paid and upon the
                  request of Aurora, GW will provide Aurora with a summary of
                  the status of development compounds and products that may be
                  used to calculate milestones.







         5.9.     PATENT DISCLAIMER. The parties acknowledge that Aurora may not
                  own or Control patent applications or patents covering the
                  manufacture, sale, use or importation of a particular compound
                  or pharmaceutical product developed and/or commercialized by
                  GW as a result of the Assay; provided, however, GW agrees to
                  pay to Aurora the milestones in Section 5.7 regardless of
                  whether a compound or pharmaceutical product is covered by a
                  patent application or patent within the Aurora Patents.

         5.10.    WITHHOLDING TAXES. All amounts required to be paid to Aurora
                  by GW pursuant to Sections 5.3, 5.6 and 5.7 of this Agreement
                  may be paid ***. At Aurora's request, GW shall provide Aurora
                  *** hereunder and shall reasonably assist Aurora to ***.
                  Should the benefit of *** not be as favourable as that
                  applying at the Effective Date then ***.


6.       INTELLECTUAL PROPERTY OWNERSHIP


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         6.1.     PRE-EXISTING INTELLECTUAL PROPERTY. This agreement does not
                  affect the ownership of Inventions, Technology and Patent
                  Rights of either party which existed prior to the Effective
                  Date.

         6.2.     INTELLECTUAL PROPERTY CREATED UNDER THE COLLABORATIVE RESEARCH
                  PROGRAM. The Assay developed by Aurora *** Collaborative
                  Research Program ***.




         6.3.     INTELLECTUAL PROPERTY CREATED THROUGH GW'S ***. Any
                  Inventions, Technology and Patent Rights relating to the
                  activities or properties of compounds discovered, identified
                  or profiled through GW's *** the Assay or other assays
                  incorporating Aurora Technology ***, subject to the terms of
                  the licenses granted by Aurora under Section 4. *** will be
                  responsible for the filing, prosecution, and enforcement of
                  all applicable patents and for the expenses thereof. Any
                  improvements, Know-How, Inventions, Technology and Patent
                  Rights developed by ***, *** for paying any fees related to
                  the filing, prosecution, and enforcement of all applicable
                  patents and for the expenses thereof.


         6.4.     TRANSFER OF RIGHTS. All rights not expressly licensed or
                  assigned by Aurora are retained by Aurora and no implied
                  licenses are conveyed herein or were conveyed before the
                  Effective Date. Except as otherwise expressly provided in this
                  Agreement, nothing in this Agreement is intended to convey or
                  transfer ownership by one party to the other of any rights,
                  title or interest in any Confidential Information, Technology,
                  copyrights or Patent Rights owned or Controlled by a party.
                  Except as expressly provided for in this Agreement, nothing in
                  this Agreement shall be construed as a license or sublicense
                  by one party to the other of any rights in any Technology,
                  copyrights, or Patent Rights owned or Controlled by a party.

         6.5.     INVENTORSHIP AND ASSIGNMENT. Inventorship of patentable
                  inventions shall be determined by U.S. patent law. GW and
                  Aurora *** Inventions, Technology and Patent Rights.

         6.6.     COPYRIGHTS. The parties agree to treat and handle, to the
                  maximum extent practical, any copyrights owned or Controlled
                  by a party in the same manner as Patent Rights owned or
                  Controlled by such party.

7.       PRODUCT DEVELOPMENT, COMMERCIALIZATION AND DILIGENCE

         7.1.     *** development and commercialization of all compounds
                  discovered through GW's ***, and such development and
                  commercialization will be at GW's sole discretion.



8.       CONFIDENTIALITY

         8.1.     CONFIDENTIAL INFORMATION. Except as expressly provided herein,
                  the parties agree


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                  that, for the term of this Agreement and *** years
                  thereafter, the receiving party shall keep completely
                  confidential and shall not publish or otherwise disclose to
                  another party and shall not use for any purpose other than
                  to perform the purposes contemplated by this Agreement any
                  Confidential Information furnished to it by the disclosing
                  party hereto pursuant to this Agreement, except that to the
                  extent that it can be established by the receiving party by
                  competent proof that such Confidential Information:

                  -        was already known to the receiving party, other than
                           under an obligation of confidentiality, at the time
                           of disclosure;
                  -        was generally available to the public or otherwise
                           part of the public domain at the time of its
                           disclosure to the receiving party;
                  -        became generally available to the public or otherwise
                           part of the public domain after its disclosure and
                           other than through any act or omission of the
                           receiving party in breach of this Agreement;
                  -        was lawfully disclosed to the receiving party by a
                           person other than a party hereto, or

                  -        was independently developed by the receiving party
                           without the use of Confidential Information.

         8.2.     PERMITTED USE AND DISCLOSURES. Each party hereto may use or
                  disclose Confidential Information disclosed to it by the other
                  party to the extent such use or disclosure is (i) reasonably
                  necessary in filing or prosecuting patent applications,
                  prosecuting or defending litigation, (ii) complying with
                  applicable law, governmental regulation or court order, (iii)
                  submitting information to tax or other governmental
                  authorities, (iv) making a permitted sublicense or (v)
                  otherwise exercising its rights hereunder, provided that if a
                  party is required to make any such disclosure of another
                  party's Confidential Information, other than pursuant to
                  subsection (ii) hereof, it will give reasonable advance notice
                  to the latter party of such disclosure, and shall obtain the
                  prior written approval of said latter party, which approval
                  shall not be unreasonably withheld.

         8.3      CONFIDENTIAL TERMS. Except as expressly provided herein, each
                  party agrees not to disclose any material or financial terms
                  of this Agreement to another party without the consent of the
                  other party, not to be unreasonably withheld; provided,
                  however, each party reserves the right to make reasonable
                  disclosures (including the redaction of material or financial
                  terms) as required by securities or other applicable laws, or
                  to actual or prospective investors or corporate partners
                  (including licensees and acquirers), or to accountants,
                  attorneys and other professional advisors on a need-to-know
                  basis under circumstances that reasonably ensure the
                  confidentiality thereof, or to the extent required by law. If
                  such Confidential Information is to become public information
                  by such disclosure the disclosing party must obtain the
                  written consent of the non-disclosing party in order to obtain
                  protection of the Confidential Information if necessary.

         8.4.     PRESS RELEASE. Notwithstanding the foregoing, the parties
                  agree that Aurora will make a press release to announce the
                  execution of this Agreement which shall be subject to prior
                  written approval of GW, such approval not to be unreasonably
                  withheld. Thereafter, GW and Aurora may each disclose to Third
                  Parties the information contained in the mutually agreed upon
                  press release without the need for further approval by the
                  other.


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9.       TERM AND TERMINATION OF THE RESEARCH COLLABORATION

         9.1.     TERM. This Agreement shall commence on the Effective Date and
                  shall terminate on the date ***. The Collaborative Research
                  Program will terminate on *** by Aurora in accordance with
                  Section 3.3., or *** after the Effective Date, whichever is
                  first, unless extended by mutual written agreement of both
                  parties.

         9.2.     TERMINATION. Either party shall have the right to terminate
                  this Agreement at any time during the term for a material
                  breach of this Agreement by the other party, provided that the
                  non-breaching party shall have first given *** days prior
                  written notice (***days in the event of non-payment of any
                  amounts due under this Agreement) to the breaching party
                  describing such breach and stating the non-breaching party's
                  intention to terminate this Agreement if such breach remains
                  uncured, and the breaching party thereafter fails to cure same
                  within such *** day period (*** day period in the event of
                  non-payment of any amounts due under this Agreement).

         9.3.     TERMINATION *** this Agreement pursuant to Sections 3.1.1 or
                  3.1.2. All amounts paid by GW to Aurora under this Agreement
                  under Sections 5.1, 5.2 and 5.3 shall be nonrefundable.

         9.4.     EFFECT OF EXPIRATION OR TERMINATION. Except as otherwise
                  expressly provided in this Agreement, the rights and
                  obligations of the parties hereof shall terminate and be of no
                  further force or effect whatsoever upon any termination of
                  this Agreement under Section 9 hereof. Sections *** and ***,
                  hereof shall survive termination or expiration of this
                  Agreement. Upon expiration or other termination of the
                  Agreement all licenses granted will thereby terminate and
                  Materials will be destroyed or returned at the direction of
                  the parties within *** days.

10       MISCELLANEOUS

         10.1.    BINDING EFFECT; ASSIGNMENT. Except as otherwise provided
                  herein, neither this Agreement nor any interest hereunder will
                  be assignable in part or in whole *** may assign this
                  Agreement ***. This Agreement will be binding upon *** herein
                  will be deemed to *** to the extent necessary to carry out the
                  intent of this Agreement. Any assignment which is not in
                  accordance with this Section is void.





         10.2.    EFFECT OF WAIVER. No waiver of any default, condition,
                  provisions or breach of this Agreement shall be deemed to
                  imply or constitute a waiver of any other like default,
                  condition, provision or breach of this Agreement.

         10.3.    REPRESENTATIONS AND WARRANTIES OF AURORA AND GW. Each Party
                  hereby represents and warrants: Such party is duly organized
                  and validly existing and in good standing under the laws of
                  the state of its incorporation and has all requisite corporate
                  power and authority to enter into this Agreement and to carry
                  out the provisions hereof. Such party


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                  is duly authorized to execute and deliver this Agreement and
                  to perform its obligations hereunder. This Agreement is a
                  legal and valid obligation binding upon it and enforceable
                  in accordance with its terms. The execution, delivery and
                  performance of this Agreement by such party does not
                  conflict with any agreement, instrument or understanding,
                  oral or written, to which it is a party or by which it may
                  be bound, nor violate any law or regulation of any court,
                  governmental body or administrative or other agency having
                  jurisdiction over it.

         10.4     ***





                  10.4.1.  LIMITATION OF LIABILITY AND WARRANTY. NEITHER PARTY
                           SHALL BE LIABLE TO THE OTHER FOR ANY SPECIAL,
                           CONSEQUENTIAL, INCIDENTIAL, OR INDIRECT DAMAGES
                           ARISING OUT OF THIS AGREEMENT, HOWEVER CAUSED,
                           UNDER ANY THEORY OF LIABILITY. Except as expressly
                           set forth in this Agreement, Aurora MAKES NO
                           REPRESENTATIONS AND EXTENDS NO WARRANTIES OF ANY
                           KIND, EITHER EXPRESS OR IMPLIED. THERE ARE NO
                           EXPRESS OR IMPLIED WARRANTIES OF MERCHANTABILITY
                           OR FITNESS FOR A PARTICULAR PURPOSE, OR THAT THE
                           USE OF THE LICENSED PRODUCTS OR SERVICES WILL NOT
                           INFRINGE ANY PATENT, COPYRIGHT, TRADEMARK, OR
                           OTHER RIGHTS OR ANY OTHER EXPRESS OR IMPLIED
                           WARRANTIES.

                  10.4.2.  ***





                  10.4.3.  ***


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         10.5.    FORCE MAJEURE. Neither party shall lose any rights hereunder
                  or be liable to the other party for damages or losses (except
                  for payment obligations) on account of failure of performance
                  by the defaulting party if the failure is occasioned by war,
                  strike, fire, act of God(s), earthquake, flood (including El
                  Nino and La Nina), lockout, embargo and governmental acts or
                  orders or restrictions.

         10.6.    AMENDMENT. No modification, supplement to or waiver of this
                  Agreement or any Addendum hereto or any of their provisions
                  shall be binding upon a party hereto unless made in writing
                  and duly signed by an authorized representative of both GW and
                  Aurora. In no event may the terms of this Agreement be
                  changed, deleted, supplemented or waived by any notice,
                  purchase order, receipt, acceptance, bill of lading or other
                  similar form of document. A failure of either party to
                  exercise any right or remedy hereunder, in whole or in part,
                  or on one or more occasions, shall not be deemed either a
                  waiver of such right or remedy to the extent not exercised, or
                  of any other right or remedy, on such occasion, or a waiver of
                  any right or remedy on any succeeding occasion.

         10.7.    ENTIRE AGREEMENT. This Agreement and each supplemental written
                  agreement contemplated hereunder, sets forth the entire
                  understanding and agreement of the parties as to the subject
                  matter thereof, and there are no other understandings,
                  representations or promises, written or verbal, not set forth
                  herein or on which either party has relied. If any provisions
                  of any such Addendum or supplemental written agreement
                  conflict with any provisions set forth in this Agreement, the
                  provisions of this Agreement shall take precedence, unless
                  such Addendum or supplemental written agreement expressly
                  refers to the specific provision(s) of this Agreement that it
                  is intended to replace or modify (and which shall be limited
                  in force and effect to such Addendum or supplemental written
                  agreement only).




         10.8.    NOTICES. All Notices under this Agreement shall be given in
                  writing and shall be addressed to the parties at the following
                  addresses:

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                                    Glaxo Wellcome House West,
                                    Berkeley Avenue,
                                    Greenford, Middlesex UB6 ONN,
                                    United Kingdom

                           FOR AURORA:
                                    Harry Stylli, Ph.D.
                                    Senior Vice President Commercial Development
                                    Aurora Biosciences Corporation
                                    11010 Torreyana Road
                                    San Diego, CA.  92121

                                    COPIES TO:
                                    John D. Mendlein, Ph.D., J.D.
                                    Senior Vice President, Intellectual Property
                                    and Chief Knowledge Officer
                                    Aurora Biosciences Corporation
                                    11010 Torreyana Road
                                    San Diego, CA.  92121

          Notices shall be in writing and shall be deemed delivered when
          received, if delivered by a courier, or on the second business day
          following mailing, if sent by first-class certified or registered
          mail, postage prepaid.

     10.9. GOVERNING LAW. This Agreement shall be governed by and construed in
          accordance with the laws of the State of California as those laws
          apply to California residents, without regard or giving effect to its
          principles of conflict of laws. Resolution of any disputes will be
          decided in California.

     10.10. THIRD PARTY BENEFICIARIES. This Agreement and the rights and
          obligations created hereunder are for the sole benefit of the parties
          hereto and their respective successors or assigns as may be permitted
          under the terms of this Agreement. By entering into this Agreement,
          the parties agree that they are not creating and do not intend to
          create implied or incidental rights inuring to the benefit of Third
          Parties.

     10.11. SEVERABILITY. This Agreement is intended to be severable. If any
          provision(s) of this Agreement are or become invalid, are ruled
          illegal by a court of competent jurisdiction or are deemed
          unenforceable under the current applicable law from time to time in
          effect during the term hereof, it is the intention of the parties that
          the remainder of the Agreement shall not be affected thereby and shall
          continue to be construed to the maximum extent permitted by law at
          such time. It is further the intention of the parties that in lieu of
          each such provision which is invalid, illegal, or unenforceable, there
          shall be substituted or added as part of this Agreement by such court
          of competent jurisdiction a provision which shall be as similar as
          possible, in economic and business objectives as intended by the
          parties to such invalid, illegal or unenforceable provision, but shall
          be valid, legal and enforceable.


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     10.12. HEADINGS. Captions and paragraph headings are for convenience only
          and shall not form an interpretative part of this Agreement. Unless
          otherwise specifically provided, all references to a Section
          incorporate all Sections or subsections thereunder. This Agreement
          shall not be strictly construed against either party hereto and maybe
          executed in two (2) or more counterparts, each of which will be deemed
          an original and the same instrument. Counterparts may be signed and
          delivered by facsimile, each of which shall be binding when sent, and
          in each case an original shall be sent via overnight courier. This
          Agreement will not be enforceable and shall have no effect if this
          Agreement is not executed ***.

     IN WITNESS WHEREOF, the parties have executed, by duly authorized
          representatives, this Agreement:

For Glaxo Group Limited                          For Glaxo Research and
                                                 Development Limited

By: /s/ SM Bicknell                             By: /s/ SM Bicknell
   ----------------------------                    ----------------------------

Date: 15 December 1999                           Date: 15 December 1999
     --------------------------                       -------------------------

Name: SM Bicknell                                 Name: SM Bicknell
     --------------------------                        ------------------------

Title: Assistant Secretary                        Title: Assistant Secretary
      -------------------------                         -----------------------



For Aurora Biosciences Corporation

By: /s/ Michael J. Dunn
   ---------------------------------------

Date: 12/15/99
      ------------------------------------
Name: Michael J. Dunn
      ------------------------------------

Title: Vice President Business Development
       -----------------------------------


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                                    EXHIBIT A





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                                    EXHIBIT B





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                                    EXHIBIT C


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                                  ATTACHMENT 1

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