<PAGE>

CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND
EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF
1934, AS AMENDED.

                                                                   Exhibit 10.13

                               Third Amendment To
                          Screening Services Agreement

     This Third Amendment To Screening Services Agreement (this "TRAP Third
Amendment") is made and dated as of February 14, 2001, (the "Third Amendment
Effective Date"), by and between Sanwa Kagaku Kenkyusho Co., Ltd., a Japanese
corporation ("Sanwa") and Telik Inc., a Delaware corporation ("Telik").

                                    RECITALS
                                    --------

     A.  Sanwa and Telik are parties to that Screening Services Agreement dated
as of December 20, 1996 as amended by that First Amendment to Screening Services
Agreement dated September 24, 1997 and that Second Amendment to Screening
Services Agreement dated October 29, 1998 (the "TRAP Agreement").

     B.  Sanwa and Telik are entering into a Master Amendment Agreement of even
date herewith in connection with which, as one of the conditions to Sanwa paying
Telik the amount set forth therein, the parties have agreed to execute and
deliver this TRAP Third Amendment.

     NOW, THEREFORE, in consideration of the above recitals and for other good
and valuable consideration, the adequacy and receipt of which are hereby
acknowledged, the parties hereby agree as follows:

1.  Amendments.  The TRAP Agreement is hereby amended as follows:
    -----------

    A.    Section 1.1 is hereby revised in its entirety to read as follows:

          1.1  Selected Targets.  From time to time during the term of this
          Agreement, Sanwa may notify Telik of a Sanwa Target, or pursuant to
          the terms of Section 1.5, a Third Party Target, (collectively
          "Selected Target") which Sanwa wishes to use in screening compounds
          submitted by Telik; provided, however, Sanwa may not submit more than
          [*] Selected Targets (not including Excluded Targets) during the term
          of this Agreement as set forth in Section 7.1 hereof.

    B.    Section 1.2 is hereby revised in its entirety to read as follows:

          1.2  Screening.

               (a) Within [*] of receipt of a notice from Sanwa in accordance
          with Subsection 1.1, subject to Subsection 1.3 below, Telik shall,
          based upon its knowledge of the Telik Library and using the TRAPTM
          technology, select and provide to Sanwa, or a third party pursuant to
          an Approved Agreement [*] compounds ("Initial Compounds") from the
          Telik Library that Telik believes, in its sole discretion, represent
          maximum chemical compound diversity in the Telik
                                     1.

<PAGE>

          Library. Sanwa shall, or a third party pursuant to an Approved
          Agreement may, screen each Initial Compound for selected activity in
          relation to the Selected Target and provide Telik the data resulting
          therefrom ("Initial Results"), including but not limited to the
          concentration at which each Initial Compound elicits a response
          which is 50% of the maximum response in the Selected Assay (the
          "EC50") resulting therefrom.

               (b) Promptly after receipt of the Initial Results Telik shall,
          based upon the Initial Results and using the TRAPTM Technology or any
          other search technology available to Telik, select and provide to
          Sanwa, or a third party pursuant to an Approved Agreement, [*]
          compounds ("Secondary Compounds") from the Telik Library that Telik
          believes, in its sole discretion, will exhibit the greatest likelihood
          of activity in relation to the Selected Target.  Sanwa shall, or a
          third party pursuant to an Approved Agreement may, screen each
          Secondary Compound for selected activity in relation to the Selected
          Target and provide Telik the data resulting therefrom ("Secondary
          Results"), including but not limited to the EC50 for each Secondary
          Compound.

               (c) If [*] that further screening activity is necessary, then
          based upon the Initial Results and Secondary Results and using the
          TRAPTM Technology or any other search technology available to Telik,
          Telik shall select and provide to Sanwa, or a third party pursuant to
          an Approved Agreement [*] compounds ("Tertiary Compounds") from the
          Telik Library that Telik believes, in its sole discretion, will
          exhibit the greatest likelihood of additional assay activity in
          relation to the Selected Target.  Sanwa will, or a third party
          pursuant to an Approved Agreement may, screen each Tertiary Compound
          for selected activity in relation to the Selected Target and provide
          Telik the data resulting therefrom ("Tertiary Results"), including but
          not limited to the EC50 for each Tertiary Compound.

    C.    Section 1.3 is hereby revised in its entirety to read as follows:

          1.3  Excluded Targets.  Notwithstanding anything herein to the
          contrary, Telik shall not be obligated to perform any of the services
          described in Section 1.2 with respect to any proposed Selected Targets
          that Telik determines are identical to or in conflict with biological
          targets included in any research collaboration between Telik and a
          third party corporate entity or any other biological targets which
          Telik is already actively pursuing, prior to receipt of a notice
          pursuant to Section 1.1 or Section 1.5 identifying such Selected
          Target ("Excluded Targets"). Telik shall notify Sanwa if a proposed
          Selected Target is an Excluded Target promptly after receipt of
          Sanwa's notice under Section 1.1 or Section 1.5 relating thereto.

                                     2.

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND
EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF
1934, AS AMENDED.

<PAGE>

    D.    Section 1.4 is hereby revised to read as follows:

          1.4  Lead Optimization

               (a) Telik shall diligently undertake a maximum of [*] Lead
          Optimization Projects (as defined below) concurrent for Sanwa at any
          given time, each with respect to a Family of Compounds (as defined
          below) as Sanwa shall select by providing written notice to Telik.
          For a period of [*] commencing on [*], Telik shall undertake, [*], a
          Lead Optimization Project for the [*] Family of Compounds.  If Telik
          completes such Lead Optimization Project in less than [*], or if Sanwa
          notifies Telik that it wishes to substitute another Lead Optimization
          Project in place of a previously selected Lead Optimization Project,
          Telik shall undertake such new or substitute Lead Optimization Project
          as Sanwa may select, taking into account the scientific advice of the
          "RMC," as such term is defined in the Collaboration Agreement between
          Telik and Sanwa dated December 20, 1996, as amended ("Collaboration
          Agreement"), by providing written notice to Telik, until the
          expiration of the above [*] period [*]. Telik shall also diligently
          undertake concurrent with the Lead Optimization Project for the [*]
          Family of Compounds a [*] Lead Optimization Project as selected by
          Sanwa including, for example, a Lead Optimization Project for the [*]
          Family of Compounds. If Sanwa requests that Telik undertake a [*] Lead
          Optimization Project at any time during the [*] period described
          above, or continue a Lead Optimization Project after the expiration of
          the [*] period described above, both after taking into account the
          scientific advice of the RMC, Sanwa shall pay Telik [*], working
          through the RMC.

               (b) Upon commencement of the [*] of the Lead Optimization Project
          for the [*] Family of Compounds, Telik shall (i) devote the
          appropriate personnel, equipment and other resources as necessary to
          ensure that the Lead Optimization Project proceeds in such a manner as
          to allow Telik to apply for the patents referred to in Section 4.5 by
          the dates set forth therein and ensure the availability of Active
          Compounds and necessary information related thereto to enable Sanwa to
          use such Active Compounds in preclinical and clinical studies as soon
          as possible and (ii) identify the appropriate personnel, equipment and
          other resources as necessary to allow Telik to diligently undertake a
          [*] Lead Optimization Project. Subject to the following requirements
          with respect to a [*] Lead Optimization Project, Telik shall ensure
          [*] a [*] Lead Optimization Project that Telik shall undertake for
          Sanwa pursuant to this Section 1.4.  At any time during the term
          hereof, Sanwa may request Telik to commence work on Preliminary Tasks
          for a [*] Lead Optimization Project. In such case, Sanwa and Telik
          will discuss and attempt in good faith to reach agreement on a work
          plan and scheduling for, and Telik shall diligently undertake the
          Preliminary Tasks necessary to commence, such [*] Lead Optimization
          Project. For the avoidance of doubt, Telik will not be obligated to
          undertake a [*] Lead Optimization Project unless and until (x) the
          parties have agreed on a work plan and scheduling for such [*] Lead
          Optimization Project and (y) Telik has received from Sanwa sufficient
          funding to support such [*] Lead Optimization Project.


                                     3.

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND
EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF
1934, AS AMENDED.

<PAGE>

               (c)  For purposes of this Agreement,

                    (i)  [*] means that Family of Compounds that includes, and
               shall include, without limitation, the following: [*] and related
               analogs and homologs ("Group 1"), [*] and related analogs and
               homologs ("Group 2") and [*] and related analogs and homologs
               ("Group 3"); and

                    (ii)  [*] means that certain Family of Compounds as
               identified by [*] and related analogs and homologs.

               (d) For purposes of this Agreement, the term "Family of
          Compounds" shall mean Active Compounds that [*], and that can be
          starting candidates for Lead Optimization Projects.

               (e) For purposes of this Agreement, "Lead Optimization Project"
          shall mean a series of studies which the RMC shall agree upon and
          which, by way of example, includes identification and selection of
          Advanced Lead Compounds with similar elements as those set forth in
          Phase 1 of the Research Plan (as defined in the Collaboration
          Agreement), and Selection of Clinical Candidates as set forth in Phase
          2 of the Research Plan (as defined in the Collaboration Agreement),
          and encompasses all of the [*], that are required until one or more
          Active Compounds are discovered which Sanwa determines may be suitable
          for use in clinical studies.

               (f) For purposes of this Agreement, "Preliminary Tasks" shall
          mean planning tasks, patent searches, review of relevant research
          papers, trade publications and other materials, development of
          scheduling and task lists and other preliminary tasks necessary for
          the parties to develop a plan for and carry out a [*] Lead
          Optimization Project.

    E.    A new Section 1.5 is hereby added to the TRAP Agreement as follows:

          1.5  Third Party Targets.

               (a) Except as otherwise may be agreed in writing by the parties,
          Sanwa has the right to submit biological targets identified by third
          parties to Telik as Selected Targets pursuant to this Agreement, and
          shall submit such targets to Telik prior to Sanwa and any such third
          party entering into an Approved Agreement  ("Third Party Target").

               (b) Sanwa shall submit all proposed Third Party Targets to Telik
          as soon as reasonably possible under the circumstances relating to
          such Third Party Target and Telik agrees to treat all such Third Party
          Targets as Confidential Information for purposes of this Agreement.

               (c) With respect to all agreements, including without limitation
          screening agreements and commercialization and license agreements that
          either Sanwa or Telik proposes to enter into relating to Third Party
          Targets to be submitted as Selected Targets pursuant to this Agreement
          ("Proposed
                                     4.

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND
EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF
1934, AS AMENDED.

<PAGE>

          Agreements") the party proposing to enter into such Proposed
          Agreement shall provide the other party with information sufficient
          to gauge the timeliness, extent and seriousness of the
          commercialization effort related to compounds that may be discovered
          as a result of the screening services performed by Telik pursuant to
          this Agreement, without jeopardizing the transaction with the third
          party to such Proposed Agreement and subject always to such third
          party's written consent.

               (d) Sanwa shall provide a draft of any Proposed Agreement
          relating to the screening services to be provided by Telik pursuant to
          Section 1.2 to Telik as soon as reasonably practicable, but in any
          event prior to signature by Sanwa.  All such drafts of such Proposed
          Agreements and any Approved Agreement signed by Sanwa shall include
          the text of the provisions set forth on Exhibit A attached hereto if
          in English or, if such Proposed Agreements or Approved Agreement are
          in Japanese, a Japanese translation of the text of the provisions set
          forth on Exhibit A that shall be attached hereto as Exhibit A-1 after
          preparation by Sanwa and approval by Telik, which approval shall not
          be unreasonably withheld or delayed. Sanwa shall have the right,
          subject to the obligation in Section 1.5(c) to redact the key
          financial and commercial terms of all such Proposed Agreements.  Sanwa
          shall have no obligation to translate any draft Proposed Agreement.
          Sanwa shall also provide Telik the opportunity to meet with each third
          party signatory to a Proposed Agreement prior to Sanwa signing such
          Proposed Agreement or any binding preliminary agreements, letters of
          intent or the like.

               (e) Telik shall promptly review and within [*] provide any
          proposed revisions that Telik may have to all drafts of Proposed
          Agreements provided by Sanwa to Telik pursuant to Section 1.5 (d) to
          ensure that the provisions set forth on Exhibit A or Exhibit A-1 as
          appropriate are embodied in such Proposed Agreement and that such
          Proposed Agreement does not contain any terms that conflict with or
          are inconsistent with the terms set forth on Exhibit A or Exhibit A-1
          as appropriate. If (i) Telik does not provide Sanwa in writing with
          such revisions to a Proposed Agreement within such [*] time period, or
          (ii) Sanwa revises a Proposed Agreement to incorporate Telik's
          proposed revisions directed solely to ensuring that the provisions set
          forth on Exhibit A or Exhibit A-1 as appropriate are embodied in such
          Proposed Agreement and that such Proposed Agreement does not contain
          any terms that conflict with or are inconsistent with the terms set
          forth on Exhibit A or Exhibit A-1 as appropriate , and Telik does not
          reject Third Party Target pursuant to Section 1.3 hereof, then Sanwa
          may sign such Proposed Agreement.  Telik shall sign all Proposed
          Agreements (a) as to which Telik has not rejected the Proposed Target
          pursuant to Section 1.3, indicating that such Proposed Target is
          acceptable to Telik and (b) which contain the provisions set forth on
          Exhibit A or Exhibit A-1, as appropriate.  A Proposed Agreement signed
          by both Sanwa and Telik, or a Proposed Agreement signed by Sanwa
          pursuant to the preceding sentence will constitute an "Approved
          Agreement" for purposes of this Agreement. For the avoidance of doubt,
          Sanwa's failure to incorporate any Telik proposed revisions that are
          not directed solely to ensuring that the provisions set forth on
          Exhibit A or Exhibit A-1, as appropriate,

                                     5.

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND
EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF
1934, AS AMENDED.

<PAGE>

          are embodied in such Proposed Agreement and that such Proposed
          Agreement does not contain any terms that conflict with or are
          inconsistent with the terms set forth on Exhibit A or Exhibit A-1 as
          appropriate shall not affect the treatment of such Proposed
          Agreement as an Approved Agreement for purposes of this Agreement.

               (f) Sanwa shall have [*] to make any payments to Telik as a
          result of entering into or with respect to any Approved Agreement.

               (g) Telik may, subject to the agreement of Sanwa regarding the
          content and timing thereof and subject to the consent of the relevant
          third party, issue a press release jointly with Sanwa announcing an
          Approved Agreement. Sanwa shall not, and shall cause the relevant
          third party not to issue a press release identifying Telik, TRAP, or
          other proprietary Telik technology in any way without Telik's consent.

    F.    Sections 4.2, 4.3 and 4.4 shall be revised in their entirety to read
          as follows:

          4.2  Sanwa Territory.  Sanwa will have the exclusive rights to exploit
          the Joint Inventions and information concerning Active Compounds in
          the Sanwa Territory including, without limitation, the right to grant
          licenses to third parties to practice the Joint Inventions and develop
          and commercialize Active Compounds, without any obligation [*]. For
          purposes of this Section, "Sanwa Territory" shall mean Japan, Korea,
          Taiwan, and the People's Republic of China.

          4.3  Telik Territory.  Telik will have exclusive rights to exploit the
          Joint Inventions and information concerning Active Compounds in North
          America and South America ("Telik Territory") including, without
          limitation, the right to grant licenses to third parties to practice
          the Joint Inventions and develop and commercialize Active Compounds,
          without any obligation to make any payments to Sanwa with respect
          thereto.

          4.4  Joint Inventions.  Sanwa and Telik will [*] revenues from the
          exploitation of the Joint Inventions and information concerning Active
          Compounds in the rest of the world, will consult with one another
          prior to entering into any agreement therefore and will take
          appropriate measures to assure [*] in each case.  If either Sanwa or
          Telik has the opportunity to enter into a world-wide agreement or an
          agreement that would include, in the case of Telik countries outside
          the Telik Territory, or in the case of Sanwa, countries outside the
          Sanwa Territory to exploit in any manner all or any portion of the
          Joint Inventions and information concerning the Active Compounds or,
          in the case of Sanwa, which relates to a Third Party Target, then the
          parties shall negotiate in good faith the terms applicable to such
          agreement.

                                     6.

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND
EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF
1934, AS AMENDED.

<PAGE>

    G.    A new Section 4.5 is added to the TRAP Agreement as follows:

          4.5  Patent Applications.  Consistent with reasonable commercial
          practice and contingent on receiving the necessary biological
          information from Sanwa, Telik shall:

               (a) Use commercially reasonable best efforts to apply for one or
          more United States provisional patents for Group 1 by [*];

               (b) Apply for at least one definitive United States patent
          covered by the provisional patent described in (a) by [*];

               (c) Use commercially reasonable best efforts to apply for one or
          more United States provisional patents for Group 2 by [*];

               (d) Apply for at least one definitive United States patent
          covered by the provisional patent described in (c) by [*];

               (e) Use commercially reasonable best efforts to apply for one or
          more United States provisional patents for Group 3 by [*];

               (f) Apply for at least one United States definitive patent
          covered by the provisional patents described in (e) by [*].

    H.    Section 6.2 (f) is revised by amending the word "sublicensees" to read
          "licensees, sublicensees...."

    I.    Article 8 is hereby deleted and replaced in its entirety by the
          following:

          8.   ACCRUED RIGHTS; SURVIVING OBLIGATIONS.

               8.1  Termination of this Agreement shall not affect any accrued
               rights of either party. The terms of Articles 4, 6 and 9 shall
               survive termination of this Agreement. Except to the extent
               reasonably necessary to allow the Parties to exploit their
               respective rights pursuant to Section 4, promptly after
               termination of this Agreement, each party shall return or dispose
               of any know-how or proprietary information of the other party
               (including in the case of Telik know-how or other materials of
               third party signatories of Approved Agreements) in accordance
               with the instructions of the other party, including, without
               limitation, any compounds, assays or other biological or chemical
               materials.

2.  Defined Terms; Incorporation.  Unless otherwise expressly provided herein,
    -----------------------------
defined terms used in this TRAP Third Amendment shall have the same meaning as
set forth in the TRAP Agreement, and all terms herein shall be incorporated into
the TRAP Agreement.  From and after the Third Amendment Effective Date all
reference to the "TRAP Agreement" in all other documents delivered in connection
with the TRAP Agreement shall refer to the TRAP Agreement, as amended hereby.

                                     7.

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND
EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF
1934, AS AMENDED.

<PAGE>

3.  Counterparts: Facsimile.  This TRAP Third Amendment may be executed in
    ------------------------
counterparts and by facsimile.

     IN WITNESS WHEREOF, the parties have executed this TRAP Third Amendment
effective as of the date first set forth above.


TELIK, INC.                            SANWA KAGAKU KENKYUSHO CO., LTD.


/s/ Michael M. Wick                    /s/ Keiji Tanimoto
----------------------------------     ----------------------------------------
By: Michael M. Wick, M.D. Ph.D.        By: Keiji Tanimoto
Its: Chairman and CEO                  Its: President



                                     8.

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND
EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF
1934, AS AMENDED.

<PAGE>

                                   EXHIBIT A


SKK shall cause the following provisions to be included in any Proposed
Agreements as described in Section 1.5(e), and the defined terms set forth in
the provisions below shall have the same meaning as ascribed to them in the
Screening Services Agreement. Where the term [Third Party] appears, SKK shall
substitute the name of the other party to the relevant Proposed Agreement.

     "Restrictions on Use." Without prior written consent of SKK or Telik,
     [Third Party] shall not use any of the Initial, Secondary or Tertiary
     Compounds or any of the information to be provided by SKK to [Third Party]
     relating to the identity of the Active Compounds for the relevant targets,
     or the chemical structures of any Active Compounds, for any purposes except
     as provided by this Agreement. This Section shall survive termination of
     this Agreement."

     "SHARING OF PROPERTY RIGHTS."

     Ownership of Joint Inventions. [Third Party] acknowledges and agrees that
     the rights to any data, inventions or discoveries (whether patentable or
     not) which: (i) are related to Active Compounds that exhibit activity with
     respect to the [Third Party] Target, and (ii) arise from the activities of
     [Third Party], Telik or SKK during the term of or in connection with this
     Agreement shall be jointly owned by SKK and Telik in accordance with the
     provisions of that certain Screening Services Agreement entered into
     between SKK and Telik on December 20, 1996, as amended ("Joint
     Inventions").

     Patent Applications. [Third Party] acknowledges and agrees that Telik shall
     have the sole fight and obligation to file, prosecute and maintain all
     patent applications and patents for the Joint Inventions. [Third Party]
     shall cooperate with SKK and Telik in the registration, defense and
     enforcement of intellectual property rights relating to the Joint
     Inventions.

     Survival. This Article shall survive termination of this Agreement."

     Information Provided. [Third Party] represents and warrants that all
     documentation and other information it has conveyed or provided under this
     Agreement was, at the time it was conveyed or provided, accurate and
     complete in light of the purposes for which it was intended."


[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, IS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE
24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

                                       1.

<PAGE>

     "CONFIDENTIAL INFORMATION"

     Protection. Except to the extent expressly authorized by this Agreement or
     otherwise agreed in writing, each Party shall for the term of this
     Agreement and for [ * ] after its expiration or termination keep
     confidential and not publish, otherwise disclose or use for any purpose
     other than as provided for in this Agreement any Confidential Information
     (defined below) furnished to it by the other Party, unless the receiving
     Party can demonstrate by adequate written documentation that such
     Confidential Information:

     (a)  was already known to the receiving Party, other than under an
          obligation of confidentiality, at the time of disclosure;

     (b)  was generally available to the public or otherwise part of the public
          domain at the time of its disclosure to the receiving Party;

     (c)  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 an obligation of
          confidentiality;

     (d)  was disclosed to the receiving Party, other than under an obligation
          of confidentiality to a third party, by a third party who had no
          obligation to the disclosing Party not to disclose such information to
          others; or

     (e)  was independently discovered or developed by the receiving Party
          without the use of Confidential Information belonging to the
          disclosing Party.

     Authorized Disclosure. Each Party may disclose Confidential Information
     belonging to the other Party to the extent such disclosure is reasonably
     necessary in the following instances:

     (a)  filing or prosecuting patents relating to clinical candidates or,
          licensed products;

     (b)  regulatory filings;

     (c)  prosecuting or defending litigation;

     (d)  complying with applicable governmental regulations;

     (e)  conducting preclinical or clinical trials of clinical candidates;

     (f)  disclosure to affiliates, employees, consultants, or agents each of
          whom prior to disclosure must be bound by similar obligations of
          confidentiality and non-use at least equivalent in scope to those set
          forth in this Section __; and,

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, IS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE
24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

                                       2.

<PAGE>

     (g)  disclosure to investment bankers; provided, however, that no such
          disclosure shall be made of SKK Confidential Information without its
          written consent, which consent shall not be unreasonably withheld.

     Notwithstanding the foregoing, in the event a Party is required to make a
     disclosure of the other Party's Confidential Information pursuant to this
     Section ---- it will, except where impracticable, give reasonable advance
     notice to the other Party of such disclosure and use its best efforts to
     secure confidential treatment of such information. In any event, the
     Parties agree to take all reasonable action to avoid disclosure of
     Confidential Information. For the avoidance of doubt, no provision in this
     Agreement shall in any manner limit or restrict Sanwa's ability to disclose
     to Telik any information conveyed to SKK by [Third Party] relating to any
     data, inventions or discoveries (whether patentable or not) which are
     related to Active Compounds and arise from the activities of [Third Party],
     SKK or Telik during the term hereof.

     Scope. In this Agreement, "Confidential Information" means any and all
     knowledge, know-how, screening results, compound structures, practices,
     processes, trade secrets and such other information as the disclosing Party
     maintains as confidential.

     Survival. This Article shall survive the expiration of this Agreement in
     accordance with paragraph -- hereof."

     "Entirety of Agreement." This Agreement embodies the entire, final and
     complete agreement and understanding between the Parties and replaces and
     supersedes all prior discussions and agreements between them with respect
     to its subject matter except as expressly stated herein. No modification or
     waiver of any terms or conditions hereof shall be effective unless made in
     writing and signed by a duly authorized representative of each Party."

SKK shall have the option, exercisable in its reasonable discretion, to use any
one of the following three alternative provisions in any Proposed Agreement with
a Third Party:

Alternative 1:

     "Assignment." Except as otherwise provided in this Section, neither Party
     may assign its rights or obligations under this Agreement without the prior
     written consent of the other Party, such consent not to be unreasonably
     withheld, except that a Party may assign its rights or obligations to a
     third party in connection with the merger, consolidation, reorganization or
     acquisition of stock or assets affecting substantially all of the assets or
     actual voting control of the assigning Party. This agreement shall be
     binding upon the successors and permitted assigns of the Parties. Any
     attempted delegation or assignment not in accordance with this Section
     shall be of no force or effect."

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, IS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE
24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

                                       3.

<PAGE>

Alternative 2:

     "Assignment." Except as otherwise provided in this Section, neither Party
     may assign its rights or obligations under this Agreement without the prior
     written consent of the other Party, such consent not to be unreasonably
     withheld, except that SKK may assign its rights or obligations to a third
     party in connection with the merger, consolidation, reorganization or
     acquisition of stock or assets affecting substantially all of the assets or
     actual voting control of SKK. This agreement shall be binding upon the
     successors and permitted assigns of the Parties. Any attempted delegation
     or assignment not in accordance with this Section shall be of no force or
     effect."

Alternative 3:

     "Assignment." Except as otherwise provided in this Section, neither Party
     may assign its rights or obligations under this Agreement without the prior
     written consent of the other Party. This agreement shall be binding upon
     the successors and permitted assigns of the Parties. Any attempted
     delegation or assignment not in accordance with this Section shall be of no
     force or effect."

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, IS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE
24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

                                       4.