<PAGE>   1
                                            * TEST OMITTED AND FILED SEPARATELY
                                               CONFIDENTIAL TREATMENT REQUESTED
                                           UNDER 17 C.F.R. SS.SS. 200.80(b)(4),
                                                           200.83 AND 240.24b-2




                                  EXHIBIT 10.43





                                LICENSE AGREEMENT

                                     BETWEEN

                                XENOMETRIX, INC.

                                       AND

                        PHASE-1 MOLECULAR TOXICOLOGY INC.






PHASE-1 XENO License Agreement           1
<PAGE>   2
                                LICENSE AGREEMENT

This Agreement is made this 27th day of July 1998 (the "Effective Date"), by and
between Xenometrix, Inc. ("XENO"), a Delaware corporation with principal offices
at 2425 55th Street, Boulder, CO 80301-5700 and Phase-1 Molecular Toxicology
Inc. ("PHASE-1"), a Delaware corporation with principal offices at 1217 Parkway
Drive, Santa Fe, New Mexico 87505-7234 to license certain technology.

                                    RECITALS

WHEREAS, XENO is the owner or exclusive licensee of the XENO Patents relating to
certain assays, technology and intellectual property further described herein,
and desires to non-exclusively license the same to PHASE-1; and

WHEREAS, PHASE-1 seeks to obtain certain non-exclusive license rights under the
XENO Patents, according to the terms contained herein (the "Agreement");

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

1.   DEFINITIONS

     1.1. "Affiliate" means any corporation or other business entity controlled
          by, or in common control of an entity. Control, as used in the context
          of a business entity, means the ownership directly or indirectly of
          fifty percent (50%) of the voting securities of the person,
          corporation, or other entity or a fifty percent (50%) or greater
          interest in the income of such corporation or other entity or the
          ability otherwise of the entity to secure that the affairs of such
          person, corporation or other entity are managed in accordance with the
          such entity's wishes.

     1.2. "Confidential Information" means any and all product, process,
          technical, marketing, financial, business, or other information, ideas
          or know-how identified as confidential information of a party to this
          agreement ("Confidential Information"), subject to the exceptions set
          forth in Section 5.1. For purposes of this Section 1.2, Materials
          owned or otherwise controlled by a party to this Agreement shall be
          deemed to be Confidential Information of such party.

     1.3. "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.


PHASE-1 XENO License Agreement           2
<PAGE>   3

     1.4. "Field" means [ * ].

     1.5. "Harvard License Agreement" means the license agreement between the
          President and Fellows of Harvard College and Venmark Ltd., now XENO,
          executed on January 17, 1992 attached hereto as Exhibit B.

     1.6. "Licensed Product(s)" means products or components thereof claimed in
          XENO Patents or products or components thereof made in accordance with
          or by means of Licensed Processes.

     1.7. "Licensed Process(es)" means the processes claimed in XENO Patents.

     1.8. "Licensed Service(s)" means services performed on a commercial basis
          for third parties or components thereof utilizing Licensed Product(s)
          or Licensed Process(es) as defined herein.

     1.9."Materials" means any biological or chemical entity for screening or
          assays, including reagents, cells, promoters, enhancers, vectors,
          plasmids, proteins and fragments thereof, peptides, antigens,
          antibodies, antagonists, agonists, inhibitors, and chemicals.

     1.10."Net Sales" means the amounts received for sales or use of Licensed
          Products or Licensed Processes less: customary trade, quantity or cash
          discounts actually allowed and taken; amounts repaid or credited by
          reason of rejection or return; and/or to the extent separately stated
          on purchase orders, invoices or other documents of sale, taxes levied
          on and/or other governmental charges made as to production, sale,
          transportation, delivery or use and paid by or on behalf of PHASE-1.

          If Licensed Product(s) or Licensed Process(es) are sold separately as
          a stand-alone product(s) or service(s), and in addition, in
          combination with another product(s) or process(es) not claimed in the
          XENO Patents, "Net Sales" for purposes of determining royalties on the
          combination product shall be calculated by multiplying sales price of
          the combination product by the fraction A/A+B where A is the price of
          the Licensed Product(s) or Licensed Process(es) sold separately and B
          is the price of the other


* CERTAIN CONFIDENTIAL MATERIAL CONTAINED IN THIS DOCUMENT HAS BEEN OMITTED AND
FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE
24B-2 OF THE SECURITIES AND EXCHANGE COMMISSION ACT OF 1934, AS AMENDED.


PHASE-1 XENO License Agreement           3

<PAGE>   4

          product(s) or process(es) in the combination product sold separately.
          If the other product(s) or process(es) in combination is (are) not
          sole separately, "Net Sales" for purposes of determining royalties
          shall be calculated by multiplying sales price of the combination
          product by the fraction A/C where A is the price of the Licensed
          Product(s) or Licensed Process(es) sole separately and C is the price
          of the combination product.


     1.11."XENO Patents" means the U.S. patents and patent applications listed
          on Exhibit A hereto, any patent applications filed prior or subsequent
          to the Effective Date that claim the benefit of an early filing date
          to any of the patent applications listed in Exhibit A, and any
          reissues, extensions, substitutions, confirmations, re-registrations,
          re-examinations, continuations, divisionals or continuations-in-part
          of the foregoing patents and patent applications, as well as all
          foreign counterparts or equivalents thereof.

     1.12."Third Party" means any entity other than (i) PHASE-1 and any of its
          Affiliates, and (ii) XENO and any of its Affiliates.

2.   LICENSES

     2.1. Grant of Licenses Under the XENO Patents from XENO to PHASE-1.

         2.1.1.Non-Exclusive License to XENO Patents. XENO hereby grants to
               PHASE-1 and its Affiliates a non-exclusive, worldwide license,
               without the right to sub-license, in the Field under XENO's
               ownership interest in the XENO Patents to make, use, have made,
               sell, have sold, offer for sale, import, export or otherwise
               exploit any process, composition of matter or other invention
               claimed in the XENO Patents.

         2.1.2.Non-Exclusive Sub-license to XENO Patents under the Harvard
               License Agreement. XENO hereby grants to PHASE-1 and its
               Affiliates a non-exclusive, worldwide sub-license, without the
               right to sub-license, in the Field under XENO's right to
               sub-license the XENO Patents in the Harvard License Agreement to
               make, use, have made, sell, have sold, offer for sale, import,
               export or otherwise exploit any process, composition of matter or
               other invention claimed in the XENO Patents. PHASE-1 acknowledges
               the Harvard License Agreement and XENO's and PHASE-1's duties and
               obligations thereunder.

PHASE-1 XENO License Agreement           4

<PAGE>   5

3.   COMPENSATION

     3.1. Compensation for the XENO Patents License.

         3.1.1.XENO Patent Licenses and Rights. As consideration for the
               licenses and rights granted to PHASE-1 herein, PHASE-1 will pay
               to XENO:

                           a)  [ * ] upon signing of this Agreement, and [ * ].

                           b)  A royalty of [ * ] percent of Net sales of
                               Licensed Products and Licensed Services in the
                               Field. Such amounts shall be paid to XENO within
                               30 (thirty) days after the end of each calendar
                               quarter and shall be creditable against the
                               minimum annual royalty pursuant to 3.1.1.c,
                               below.

                           c)  A minimum annual royalty (the "Minimum Annual 
                               Royalty") of [ * ] per year during the term of
                               this Agreement. The first such payment shall be
                               for the twelve month period (the "License Year")
                               commencing on the Effective Date of this
                               Agreement, and shall be paid to XENO within
                               thirty days after the end of the License Year. In
                               each year thereafter, Minimum Annual Royalties
                               shall be calculated for the corresponding License
                               Year and shall be payable within thirty days of
                               the end of such License Year. All quarterly
                               royalty payments paid to XENO for a given License
                               Year pursuant to 3.1.1.b, shall be creditable
                               against the Minimum Annual Royalty for that
                               License Year.

                           d)  Compensation for the XENO Patents License will be
                               due by PHASE-1 to XENO until the termination of
                               this Agreement and at the most until the last
                               expiration date of all XENO Patents.

         3.1.2.Royalty Reports, and Payments. Beginning on the Effective Date,
               PHASE-1 shall make non-audited written reports (even if there are
               no sales) and earned royalty payments to within thirty (30) days
               after the end of the each calendar quarter. These reports shall
               state the Net Sales of Licensed Product(s) and Licensed
               Service(s) during such completed calendar quarter, and resulting
               calculations of royalty payment due XENO for such completed
               calendar quarter. Concurrent with the making of each such report,
               PHASE-1 shall include payment due XENO of royalties for the
               calendar quarter covered by such report. The royalty will be
               solely due for


* CERTAIN CONFIDENTIAL MATERIAL CONTAINED IN THIS DOCUMENT HAS BEEN OMITTED AND
FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE
24B-2 OF THE SECURITIES AND EXCHANGE COMMISSION ACT OF 1934, AS AMENDED.

PHASE-1 XENO License Agreement           5
<PAGE>   6

                  the countries where there is an issued XENO Patent and where a
                  valid claim is in effect.

         3.1.3.   Accounting.  PHASE-1  agrees  to keep and  maintain  records 
                  for a period of three (3) years showing the sale, use, and Net
                  Sales according to this Agreement. Such records will include
                  general ledger records showing cash receipts and expenses, and
                  records that include sufficient detail to enable the royalties
                  payable hereunder by PHASE-1 to be determined. PHASE-1 further
                  agrees to permit its relevant books and records to be examined
                  by XENO confidentially pursuant to the provisions herein, from
                  time to time during the period of 3 years after the date of
                  the royalties report covering such records to the extent
                  necessary to verify the accuracy of such reports provided for
                  above. Such examination is to be made by XENO or its designee,
                  at the expense of XENO except in the event that the results of
                  a definitive audit reveal an underreporting of royalties due
                  XENO of five percent (5%) or more in any calendar year, then
                  the audit costs shall be paid by PHASE-1.

         3.1.4.   "Most Favored Nations" Provision. PHASE-1 fees, royalties, and
                  payment plan represent the best available to all licensees to
                  date. If more favorable terms are agreed upon for other
                  substantially similar licenses and licensees, such terms will
                  be made available to PHASE-1.


4.    REPRESENTATIONS AND WARRANTIES

     4.1. Representations and Warranties of PHASE-1 and XENO.

         Each party hereby represents and warrants:

                  Corporate Power. Such party is duly organized and validly
                  existing and in good standing under the laws of the state
                  and/or country of its incorporation and has all requisite
                  corporate power and authority to enter into this Agreement and
                  to carry out the provisions hereof.

                  Due Authorization. Such party is duly authorized to execute
                  and deliver this Agreement and to perform its obligations
                  hereunder.

                  Binding Agreement. 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

PHASE-1 XENO License Agreement           6
<PAGE>   7
                  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.

                  Third Party Rights and Interests. In addition, XENO hereby
                  represents and warrants that it has not granted and, during
                  the term of this Agreement, will not grant any rights or
                  interest to any party which is inconsistent with the rights
                  and licenses granted to PHASE-1 hereunder.

     4.2 Negation of Warranties

                  Except as expressly set forth in this Agreement, XENO 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 IMPLED WARRANTIES.

     4.3 Harvard License Agreement. XENO represents and warrants that the
         Harvard License Agreement has not at the date hereof expired, been
         terminated by either XENO or the President and Fellows of Harvard
         College and that XENO has not at the date hereof received nor given
         notice of termination for breach of the Harvard License Agreement. XENO
         represents and warrants to use all reasonable efforts to maintain the
         Harvard License Agreement, including, but not limited to complying with
         its obligations to pay the compensation due for the Harvard License
         Agreement.

     4.4 Infringement. PHASE-1 hereby agrees to notify XENO immediately of any
         claim it receives for alleged patent infringement through use of XENO
         Patents.


5.   CONFIDENTIALITY

     5.1. Confidential Information. Except as expressly provided herein, the
          parties agree that, for the Term and five (5) 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:


PHASE-1 XENO License Agreement           7
<PAGE>   8
                  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; or

                  was lawfully disclosed to the receiving party by a person
                  other than a party hereto,

                  or

                  was independently developed by the receiving party.

     5.2. 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 reasonably necessary in filing or
          prosecuting patent applications, prosecuting or defending litigation,
          complying with applicable law, governmental regulation or court order,
          submitting information to tax or other governmental authorities,
          making a permitted sublicense or 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 a confidentiality agreement, it will give reasonable
          advance notice to the latter party of such disclosure and, save to the
          extent inappropriate in the case of patent applications, will use
          reasonable efforts to secure confidential treatment of such
          information prior to its disclosure (whether through protective orders
          or otherwise).

     5.3. 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 ensure the confidentiality thereof, or to the
          extent required by law.

     5.4. Press Release. Notwithstanding the foregoing, the parties shall agree
          upon a press release to announce the execution of this Agreement.
          Thereafter, XENO and PHASE-1 may each disclose to Third Parties the
          information contained in such press release without the need for
          further approval by the other.

6.   TERMINATION

     6.1.1.This Agreement shall continue until the last expiration date of all
           patents licensed under this Agreement.


PHASE-1 XENO License Agreement           8
<PAGE>   9
     6.1.2.Either party shall have the right to terminate this Agreement at any
           time for a material breach of this Agreement by the other party,
           provided that the non-breaching party shall have first given ninety
           (90) days prior written notice (thirty (30) days in the event of
           non-payment of any amounts, including scheduled up-front fee payments
           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 thirty (30) days.

     6.1.3.PHASE-1 may terminate this Agreement without cause at any time by
           providing written notice to XENO of such termination and such
           termination will be effective ninety (90) days thereafter. Any
           termination pursuant to Section 6.1.3 shall not relieve PHASE-1 of
           any obligation or liability accrued hereunder prior to such
           termination, including PHASE-1's obligation to pay royalties accrued
           or accruable. The licenses granted under this agreement shall
           terminate in the event the Agreement is terminated by PHASE-1 or by
           XENO for an uncured breach by PHASE-1.

7.   MISCELLANEOUS

     7.1. Binding Effect; Assignment. This Agreement shall be binding upon the
          parties' respective successors and permitted assigns. Neither party
          may assign this Agreement or any of its rights or obligations
          hereunder without the prior written consent of the other party (not to
          be unreasonably withheld), and any such attempted assignment shall be
          void; provided, that PHASE-1 and XENO may assign this Agreement as
          part of a merger or consolidation in which the surviving entity
          assumes all of PHASE-1's and XENO's rights and obligations hereunder
          or a sale of substantially all of the assets of such party to which
          this Agreement relates. PHASE-1 shall have no rights to transfer or
          sublicense this Agreement except as part of a merger or consolidation
          as described above. The parties agree that in the event of the
          termination of the Harvard License Agreement, the President and
          Fellows of Harvard College shall have the option of having this
          Agreement assigned to it or terminating the licenses granted herein.

     7.2. 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.

     7.3. Limitation of Liability. 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.


PHASE-1 XENO License Agreement           9
<PAGE>   10
     7.4. Indemnification. PHASE-1 will defend, indemnify and hold XENO, its
          officers, directors, employees, Affiliates and agents harmless against
          any and all liability, loss, damage, claim or expense (including
          attorney's fees) arising out of a suit by a Third Party from the
          performance under this Agreement by PHASE-1; except to the extent such
          claim is caused by the negligence or willful misconduct of XENO or a
          breach of a representation of XENO. XENO will defend, indemnify and
          hold PHASE-1, its officers, directors, employees, Affiliates and
          agents harmless against any and all liability, loss, damage, claim or
          expense (including attorney's fees) arising out of a suit by a Third
          Party from the performance under this Agreement by XENO; except to the
          extent such claim is caused by the negligence or willful misconduct of
          PHASE-1 or a breach of a representation of PHASE-1.

     7.5. Patent Defense Costs. XENO will use reasonable efforts, at its
          discretion, to enforce XENO patents at its own expense against any
          Third Party infringement. PHASE-1 at its option and at its expense may
          elect to join in any prosecution of a Third Party infringer of the
          XENO Patents in the Field initiated by XENO. In the event that PHASE-1
          is sued by a Third Party for infringement of a Third Party's patent,
          XENO hereby agrees, if PHASE-1 so requests, to provide PHASE-1 with
          all reasonable advice or technical support that PHASE-1 may reasonably
          request at PHASE-1's expense.

     7.6. Patent Marking. PHASE-1 agrees to mark all Licensed Product(s) and
          Licensed Process(es), if applicable, in accordance with 35 U.S.C.
          ss.287 and other applicable laws and regulations in thE territory
          where such Licensed Product(s) is (are) manufactured, used or sold or
          where such Licensed Process(es) is (are) sold. However,
          notwithstanding the options provided under 35 U.S.C. ss.287, PHASE-1
          will mark each product sold by it which could potentially be used to
          infringe the claims of the XENO patents as follows: "This product is
          sold under license from Xenometrix, Inc".

     7.7. Diligence. PHASE-1 agrees to use best efforts to fulfill the
          obligations of Section 2.2 (e) of the Harvard License Agreement as a
          sublicensee of XENO under the Harvard License Agreement.

     7.8. 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,
          earthquake, flood, lockout, embargo, governmental acts or orders or
          restrictions, failure of suppliers, or any other reason where failure
          to perform is beyond the reasonable control and not caused by the
          negligence or intentional conduct or misconduct of the nonperforming
          party, and such party 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.


PHASE-1 XENO License Agreement           10
<PAGE>   11
     7.9.  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 XENO and PHASE-1. 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.

     7.10. Entire Agreement. This Agreement, and each Exhibit attached hereto,
           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).

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


                           For XENO:

                                    President
                                    Xenometrix, Inc.
                                    2425 North 55th Street
                                    Boulder, Colorado 80301-5700

                           For PHASE-1:
                                    President
                                    PHASE-1 Molecular Toxicology Inc.
                                    1217 Parkway Drive
                                    Santa Fe, NM 87505-7234


PHASE-1 XENO License Agreement           11
<PAGE>   12
         Notices shall be in writing and shall be deemed delivered when
         received, if delivered by a courier, overnight mail service or the
         like, or a week following mailing, if sent by first-class certified or
         registered mail, postage prepaid.

   7.12   Arbitration. The parties recognize that disputes as to certain
          matters may from time to time arise during the term of this Agreement
          which relate to either party's rights and/or obligations hereunder. It
          is the objective of the parties to establish procedures to facilitate
          the resolution of disputes arising under this Agreement in an
          expedient manner by mutual cooperation and without resort to
          arbitration. The parties agree that prior to any arbitration
          concerning this Agreement, XENO's CEO and PHASE-1's CEO will meet in
          person or by video-conferencing in a good faith effort to resolve any
          disputes concerning this Agreement. Within thirty (30) days of a
          formal request by either party to the other, any party may, by written
          notice to the other, have such dispute referred to their respective
          officers designated or their successors, for attempted resolution by
          good faith negotiations, such good faith negotiations to begin within
          thirty (30) days after such notice is received. Except as otherwise
          provided specifically herein, any controversy or claim under this
          Agreement shall be solely settled by arbitration by one arbitrator
          pursuant to the Commercial Arbitration Rules of the American
          Arbitration Association (the "Association"); provided that the parties
          shall first use their best efforts to resolve such dispute by
          negotiation. The arbitration shall be conducted in Boulder, Colorado.
          The arbitrator shall be selected by the joint agreement of the
          parties, but if they do not so agree within twenty (20) days of the
          date of a request for arbitration, the selection shall be made
          pursuant to the rules of the Association. The decision reached by the
          arbitrator shall be conclusive and binding upon the parties hereto and
          may be filed with the clerk of any court of competent jurisdiction,
          and a judgment confirming such decision may, if desired by any party
          to the arbitration, be entered in such court. Each of the parties
          shall pay its own expenses of arbitration and the expenses of the
          arbitrator(s) shall be equally shared; provided, however, that if in
          the opinion of the arbitrator(s) any claim hereunder or any defense or
          objection thereto was unreasonable, the arbitrator(s) may assess, as
          part of the award, all or any part of the arbitration expenses
          (including reasonable attorneys' fees) against the party raising such
          unreasonable claim, defense or objection. Nothing herein set forth
          shall prevent the parties from settling any dispute by mutual
          agreement at any time.

   7.13         Governing Law. This Agreement shall be governed by and construed
                in accordance with the laws of the State of Colorado, without
                regard or giving effect to its principles of conflict of laws.

   7.14         Severability and Survival. 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


PHASE-1 XENO License Agreement           12
<PAGE>   13
                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. Sections 5 and 7 of this Agreement will survive the
                expiration or any other termination of this Agreement

     7.15       Independent Contractors. The parties hereto are acting as
                independent contractors and shall not be considered partners,
                joint venturers or agents of the other. Neither shall have the
                right to act on behalf of, or to bind the other.

     7.16       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 an Article incorporate all Articles or subsections
                thereunder. This Agreement shall not be strictly construed
                against either party hereto and maybe executed in two or more
                counterparts, each of which will be deemed an original and the
                same instrument.

         IN WITNESS WHEREOF, the parties have executed this Agreement.


By:   /s/Stephen J. Sullivan                           Date:  7/27/98
      ------------------------                         --------------------
      Stephen J. Sullivan
      CEO and President
      For Xenometrix, Inc.





By:   /s/ Spencer Farr                                 Date:  July 24, 1998
      ------------------------                         --------------------
      Spencer Farr, Ph.D.
      Chairman, President and CEO
      For Phase-1 Molecular Toxicology, Inc.


PHASE-1 XENO License Agreement           13
<PAGE>   14

                                    EXHIBIT A
                                 [TO BE UPDATED]

<TABLE>
<CAPTION>
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                            EUKARYOTIC GENE PROFILING
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PATENT/ APPLICATION #    FILING DATE       COUNTRY      ISSUE DATE                         TITLE
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<S>                      <C>              <C>           <C>           <C>         
      08/008,896           1/21/93           US
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      08/374,641           7/21/95           US          (Allowed     Methods and Diagnostic Kits Utilizing Mammalian
                                                         2/17/98).      Stress Promoters to Determine Toxicity of a
                                                                                          Compound
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        612434             1/21/94        Australia       6/11/98
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       E160178             1/21/94         Austria       11/12/97
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      0 680 517            1/21/94         Belgium       11/12/97
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       2154265             1/21/94         Canada
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      0 680 517            1/21/94         Denmark       11/12/97
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      0 680 517            1/21/94           EPC         11/12/97
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      0 680 517            1/21/94         France        11/12/97
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   694 06 772.5-08         1/21/94         Germany       11/12/97
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      980400301            1/21/94         Greece        11/12/97
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      0 680 517                           Hong Kong
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        E77394             1/21/94         Ireland       11/12/97
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      20035BE/98           1/21/94          Italy        11/12/97
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       6-517147            1/21/94          Japan
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      0 680 517            1/21/94       Luxembourg      11/12/97
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      0 680 517            1/21/94         Monaco        11/12/97
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      0 680 517            1/21/94       Netherlands     11/12/97
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      US94/00583           1/21/94           PCT
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      0 680 517            1/21/94        Portugal        1/19/98
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      9601405-5            2/13/96        Singapore
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      0 680 517            1/21/94          Spain        11/12/97
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      0 680 517            1/21/94         Sweden        11/12/97
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      0 680 517            1/21/94       Switzerland     11/12/97
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      0 680 517            1/21/94           UK          11/12/97
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</TABLE>

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