<PAGE>
                                                                   Exhibit 10.31

[*] 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 406 OF THE SECURITIES EXCHANGE ACT OF
    1933, AS AMENDED.

                             COLLABORATION AGREEMENT

THIS COLLABORATION AGREEMENT (the "Agreement") is made and entered into as of
the last execution date by a Party to this Agreement ("Effective Date") by and
between EXELIXIS, INC., a Delaware corporation having a principal place of
business at 170 Harbor Way, P.O. Box 511, South San Francisco, California
94083-0511 ("Exelixis"), and CYTOKINETICS, INC., a Delaware corporation having a
place of business at 280 East Grand Avenue, South San Francisco, California
94080 ("Cytokinetics"). As used herein, references to Cytokinetics and Exelixis
shall also include their respective Affiliates.

                                   BACKGROUND

        A.     Cytokinetics is engaged in the research, development and
               commercialization of biotechnology and pharmaceutical products;

        B.     Exelixis is engaged in the research, development and
               commercialization of biotechnology, pharmaceutical, agrochemical
               and agricultural products and has developed novel proprietary
               methods for the generation of compound libraries;

        C.     Cytokinetics desires to obtain, and Exelixis desires to supply,
               certain of such compounds for screening and further evaluation
               and development by each Party, all on the terms and conditions
               set forth below.

NOW, THEREFORE, for and in consideration of the covenants, conditions, and
undertakings hereinafter set forth, it is agreed by and between the Parties as
follows:

          1.      DEFINITIONS.

                  1.1      "AFFILIATE" shall mean an entity which controls, is
controlled by or is under the common control with a Party. An entity shall be
regarded as in control of another entity for purposes of this definition if it
owns or controls more than fifty percent (50%) of the shares of the subject
entity entitled to vote in the election of directors (or, in the case of an
entity that is not a corporation, for the election of the corresponding managing
authority).

                  1.2      "COLLABORATION" shall mean a collaborative
relationship between a Party and a third party(ies), the subject of which is the
research, discovery, development, manufacturing and/or commercialization of
Pharmaceuticals.

                  1.3      "COMPOUND" shall mean each chemically distinct
compound that is synthesized by Exelixis that fulfills fee Quality Control
Criteria on a per Plate basis and is delivered to Cytokinetics in accordance
with Section 3.4.

                  1.4      "COMPOUND PATENT" shall mean patents and patent
applications covering the composition, use, or method of preparation, of any
Compound, filed after the date of synthesis of such Compound hereunder, whether
foreign or domestic, all patents arising from such applications, and all patents
and patent applications based on, or claiming or corresponding to the priority
dates, of

                                       -1
<PAGE>

any of the foregoing and any renewals, reissues, extensions, (or other
governmental actions that provide exclusive right to the owner thereof in the
patented subject matter beyond the original expiration date), substitutions,
confirmations, registrations, revalidations, reexaminations, additions,
continuations, continued prosecutions, continuations-in-part or divisions of or
to any of the foregoing, including, without limitation, supplementary protection
certificates or the equivalent thereof.

                  1.5      "CONFIDENTIAL INFORMATION" shall have the meaning as
set forth in Article 5.

                  1.6      "DESIGN CRITERIA" shall mean the criteria for the
design and/or synthesis of the Compounds as established by the JRC pursuant to
Section 3.2.

                  1.7      "DRUG PRODUCT" shall mean a composition of matter
used in the treatment, prevention or diagnosis of disease, state or condition,
which composition of matter is (i) a Compound, or (ii) derived from the use of a
Compound as [*] of such composition of matter.

                  1.8      "DRUG PRODUCT USE" shall mean use solely to research,
develop and/or commercialize a Drug Product, internally or as part of a
Collaboration, including the right to have any of the foregoing conducted on a
Party's (including Collaboration partners') behalf by a third party.

                  1.9      "EXELIXIS BACKGROUND TECHNOLOGY" shall mean Exelixis
Patent Rights and Exelixis Know-How.

                           1.9.1    "EXELIXIS PATENT RIGHTS" shall mean (i)
patents and patent applications, whether foreign, or domestic, that claim, or
are necessary or useful to exploit (A) a Compound or composition-of-matter
containing such Compound or a method of use thereof or (B) a process developed
prior to the Effective Date and/or under the Research Program, in each case, for
the synthesis of Compounds (or analogs or derivatives thereof as provided in
Section 4.2.2), and (ii) any divisions, continuations, continuations-in-part,
reissues, reexaminations, or extensions to the extent the same have an earliest
effective filing date prior to the date described in (i) above, and any (iii)
substitutions, confirmations, registrations, or revalidations of any of the
foregoing, in each Case, which are owned or controlled by Exelixis (solely or
jointly), to the extent Exelixis has the right to license or sublicense the
same.

                           1.9.2    "EXELIXIS KNOW-HOW" shall mean synthetic
protocols developed prior to the Effective Date and/or under the Research
Program, in each case, which are necessary or useful for the synthesis of the
Compounds (or analogs or derivatives thereof as provided in Section 4.2.2), and
any technical information, know-how, process, procedure, composition, method,
formula, technique, software, design, drawing or data directly relating to the
Compounds or necessary or useful for the manufacture, use or exploitation
thereof.

                  1.10     "INTERNAL RESEARCH USE" shall mean use solely for
research and/or pharmaceutical lead discovery purposes, internally or as part of
a Collaboration, including the right to have any of the foregoing conducted on a
Party's (including Collaboration partners') behalf by a

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third party; provided, it is understood and agreed that such use shall exclude
the right to develop and/or commercialize the Compounds.

                  1.11     "PARTY" OR "PARTIES" shall mean individually
Exelixis, Cytokinetics or an Affiliate of the same, and collectively, Exelixis,
Cytokinetics and their Affiliates.

                  1.12     "PLATE" shall have the meaning as set forth in
Appendix B.

                  1.13     "PROGRAM COMPOUND INFORMATION" shall mean data,
methods, results, conclusions, information and/or deliverables generated in
connection with the design and/or production of the Compounds under the Research
Program that are necessary for a person trained in the art of compound synthesis
to make the Compounds, including without limitation, Design Criteria, structure,
composition, results from Quality Control Criteria analysis of each Compound by
[*], methods of synthesis, synthons, and non-commercially available building
blocks relating to the Compounds.

                  1.14     "QUALITY CONTROL CRITERIA" OR "QCC" shall mean the
quality control criteria established by the Parties as described in Appendix B,
as may be amended by the JRC from time to time.

         2.       RESEARCH PROGRAM.

                  2.1      GENERAL. Cytokinetics and Exelixis will conduct a
research program on a collaborative basis with the principal goal of producing a
high throughput screen library consisting of up to a total of [*] ([*])
Compounds (the "Research Program"). The Research Program shall be conducted in
accordance with the Design Criteria as established by the JRC, unless otherwise
agreed by the Parties in writing. Each Party agrees to keep the other Party
informed of its progress and activities within the Research Program. The
scientific scope of the Research Program is further described in Appendix A,
attached hereto, as may be amended in writing by the JRC from time to time under
Section 3.2.

                  2.2      LIBRARY. Exelixis shall diligently utilize its
combinatorial Chemistry expertise and apply its related technologies, as
directed by the JRC, to generate the Compounds on behalf of the Parties.
Exelixis shall be responsible for all components of library production,
analytics, informatics and formatting.

                  2.3      NOVEL COMPOUNDS. Exelixis and Cytokinetics shall each
use their respective diligent efforts to design Compounds that are not covered
by any Exelixis or Cytokinetics intellectual property either (i) existing as of
the Effective Date and excluded from the Research Program or (ii) arising
outside of the Research Program during the Term (as defined in Section 8.1) that
is owned, assigned and/or licensed by Exelixis or Cytokinetics. Without limiting
the foregoing, each Party shall use its diligent efforts to not (i) design
and/or synthesize any Compounds under this Agreement that have been, or are in
the process of being, designed and/or synthesized under any other
collaboration(s) it has with a third party, and/or (ii) design and/or synthesize
any other compounds under any other collaboration(s) it has with a third party
that have been, or are in the process of being, designed and/or synthesized as a
Compound under this Agreement.

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  omitted portions.

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<PAGE>

                  2.4      PERSONNEL. In accordance with Section 5.1, Exelixis
may disclose to employees and personnel of Exelixis (each, a "Research Program
Personnel"), on a need to know basis under circumstances that ensure the
confidentiality thereof, information within the Program Compound Information,
including any Cytokinetics Confidential Information, Design Criteria, and/or
Quality Control Criteria included therein, solely to conduct their designated
activities under the Research Program. Exelixis may disclose to third parties
who are under contractual relationship with Exelixis to synthesize scaffolds
and/or generic structures (each a "Exelixis Third Party Supplier") information
within the Program Compound Information (but excluding Design Criteria, Quality
Control Criteria, specific structures or compositions of the Compounds to be
produced hereunder, or results from Quality Control Criteria analysis of the
Compounds by [*]) to the extent necessary for such Exelixis Third Party
Supplier to perform its activities as described hereunder. Any Exelixis Third
Party Supplier performing such activities shall be under a confidentiality
agreement with Exelixis on terms no less restrictive than the confidentiality
provisions of this Agreement.

                  2.5      NO CONFLICTING ACTIVITIES. During the Term of this
Agreement, Exelixis shall not, and shall ensure that the Research Program
Personnel shall not, conduct the Research Program in conjunction with any other
projects being conducted at, or on behalf of, Exelixis that would (a) conflict
with any of the provisions of this Agreement, or (b) preclude Exelixis from
complying with the provisions hereof. In addition, Exelixis shall not enter into
agreements with Exelixis Third Party Suppliers that conflict with any of the
provisions of this Agreement and shall use diligent efforts to ensure compliance
with the confidentiality provisions, documentation requirements and intellectual
property rights provisions of this Agreement.

                  2.6      RECORDS. In connection with the performance of the
Research Program, Exelixis shall ensure that the Research Program Personnel who
perform such services shall maintain laboratory notebooks, records and data
("Records") in accordance with good laboratory and research practices.

                  2.7      REPORTS. Exelixis shall promptly provide to the JRC
documentation as to the Compounds, Program Compound Information, Records,
methods, results, conclusions, information and/or other deliverables made,
conceived, reduced to practice or otherwise generated in connection with this
Agreement ("Reports"). All Reports, Records, including any required laboratory
notebooks, records and data pursuant to any research services conducted under
the Research Program, shall be [*] by [*] and [*], shall be treated in all
respects as [*] Confidential Information of [*] and [*], and [*] shall have the
right to disclose, use and exploit such information in conjunction with its
disclosure, use and exploitation of the Compounds and Program Compound
Information in accordance with Article 4. The JRC shall deliver to Cytokinetics
such documentation from time to time and Without request by Cytokinetics.

                  2.8      FURTHER ASSURANCES. Exelixis shall provide to
Cytokinetics documentation reasonably requested by Cytokinetics in order to
assist Cytokinetics in determining whether any Compounds, Program Compound
Information, Plates, Records, Reports, and/or other deliverables comply fully
with this Article 2, Article 3 and Appendices A and B.

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<PAGE>

         3.       RESEARCH PROGRAM OVERVIEW.

                  3.1      JOINT RESEARCH COMMITTEE. Promptly after the
Effective Date, the Paries shall establish a six (6) member committee (the
"Joint Research Committee" or "JRC") composed of three (3) representatives from
each Party to manage the Research Program. Each representative of the JRC shall
have one (1) vote. All decisions of the JRC shall be made by unanimous vote. In
the event a unanimous decision can not be reached, then either Party may, by
written notice to the other Party, have such issue referred to the [*] of
Cytokinetics and Exelixis, [*] and [*], respectively, for resolution by good
faith negotiations within thirty (30) days after such notice is received.
Minutes of the JRC shall be taken, and shall, at a minimum, record all decisions
made. Such minutes shall be approved by both Parties. Each Party may replace its
appointed JRC representatives at any time upon written notice to the other
Party.

                  3.2      JRC RESPONSIBILITIES. The JRC shall be responsible
for planning, overseeing, reviewing and coordinating the work being done under
the Research Program, including; (i) making decisions regarding the specific
details of templates and Compounds for synthesis, including without limitation
the Design Criteria for the Compounds; (ii) evaluating progress against
timelines established by the JRC for the Research Program, including without
limitation the design, quality assurance testing and delivery of Compounds;
(iii) establishing and monitoring the schedule for delivery of Compounds; (iv)
establishing, maintaining and updating on an ongoing basis a database record of
the design of each of the Compounds and each Party's contribution to such
design, as further described in Section 4.3.2; (v) recording and approving
meeting minutes; and (vi) having the authority to accept or reject any Plates
and/or Compound(s) synthesized that failed the Quality Control Criteria
established by the Parties as set forth in Appendix B attached hereto, as may
be amended in writing by the JRC from time to time.

                  3.3      MEETINGS. The JRC shall meet quarterly, or as more or
less often as otherwise mutually agreed by the Parties, at such locations as the
Parties agree. It is understood that such meetings shall be held at least
quarterly in person, otherwise by telephone, in writing or by electronic mail.
The JRC shall provide monthly written updates to each Party as to the progress
of the Research Program.

                  3.4      DELIVERABLES.

                           3.4.1    COMPOUNDS. Exelixis shall deliver to
Cytokinetics, in accordance with the timelines as established by the JRC, the
number of unique Compounds as set forth in Table 1 below, such Compounds to be
delivered in Plates in accordance with the provisions of Appendices A and B:

Table 1:

<TABLE>
<CAPTION>
Year      No. Of Compounds
----      ----------------
<S>       <C>
[*]             [*]
[*]             [*]
[*]             [*]
[*]             [*]
[*]             [*]
Total:          [*]
</TABLE>

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The JRC shall use diligent efforts to establish the Design Criteria for the
Compounds, and schedule the synthesis thereof, such that the Plates will be
delivered to Cytokinetics on a regular basis, with the goal of making such
deliveries [*], but in no event [*] (with goal of each such delivery equaling
approximately [*] if [*] (and [*] if [*]) of the total amount of Compounds
scheduled to be delivered in such year), or, as may be mutually agreed by the
Parties, on an alternative schedule.

Exelixis shall deliver Plates to Cytokinetics promptly following the synthesis
and quality assurance testing of the Compounds formatted thereon; provided,
Exelixis shall use diligent efforts to complete such synthesis, quality
assurance testing, and delivery of Plates within [*] ([*]) months after the JRC
has established the Design Criteria of the Compounds formatted thereon. In the
event Exelixis is unable to maintain such scheduled synthesis, quality assurance
testing, and/or deliveries it shall provide Cytokinetics with prompt written
notice thereof.

                           3.4.2    PLATE FORMAT. All Compounds shall be
formatted according to Appendix A; provided, that if requested by Cytokinetics,
Exelixis may deliver a format that consists of [*] ([*]) compounds per
Plate. Other formats proposed by Cytokinetics shall be reviewed and agreed in
writing by the JRC. Any additional final custom formatting for Cytokinetics'
purpose shall be performed at Cytokinetics.

                           3.4.3   ACCEPTANCE/REJECTION/RESYNTHESIS/REPLACEMENT
OF PLATE(S). All Plates that fulfill the Quality Control Criteria set forth in
Appendix B and are delivered to Cytokinetics shall be deemed accepted ("Accepted
Plates"). Plates that do not fulfill Quality Control Criteria will be reviewed
by the JRC and accepted, rejected or designated for re-synthesis by the JRC. If
a Plate is accepted by the JRC, the compounds on such Plate shall be considered
to have met the Quality Control Criteria and shall be deemed Compounds. If a
Plate is rejected, upon agreement with the JRC, the entire Plate may be
resynthesised. The re-synthesis of Plates shall not involve either reformatting
of compounds, removal or replacement of compounds. Exelixis shall promptly
notify the JRC of the existence of any excess template material. Any excess
template material shall [*] the Parties and made available to each of the
Parties within a reasonable time after the JRC's receipt of such notification
from Exelixis. With respect to Plates, and/or compounds synthesized by Exelixis
under the Research Program which are rejected by the JRC, the JRC shall
determine whether such Plates and/or compounds, including any related Program
Compound Information, shall be destroyed and/or [*] between the Parties. It is
understood and agreed, that neither Party shall have the right to disclose, use
and/or exploit such rejected Plates and/or compounds, including any related
Program Compound Information, except as expressly authorized by the JRC in
writing. In the event that the Plate(s) delivered to Cytokinetics contain
Compound(s) that do not substantially match with the Program Compound
Information supplied by Exelixis, Cytokinetics shall notify Exelixis within [*]
thereof, and Exelixis shall promptly replace such Plate(s) with Plate(s) of
Compounds substantially matching such Program Compound Information, [*] to
Cytokinetics. Notwithstanding the above, Exelixis shall not be responsible for
losses resulting from, relating to or arising from (i) acts or omissions or the
gross negligence or willful misconduct of Cytokinetics or (ii) damage to Plates
or Compounds that occur after delivery to Cytokinetics.

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                           3.4.4    PROGRAM COMPOUND INFORMATION. At the time of
delivery of each Plate, Exelixis shall deliver to Cytokinetics Program Compound
Information substantially relating to each Compound contained on such Plate.
Exelixis and Cytokinetics will diligently work to define a suitable electronic
format, and subject to electronic file format compatibility, Exelixis shall make
the Program Compound Information available in electronic files for batch
registration as set forth in Appendix B.

                           3.4.5    OTHER DELIVERABLES. Without limiting the
foregoing, Exelixis shall deliver to Cytokinetics the deliverables set forth on
Appendix A in accordance with the time schedules set forth therein.

         4.       OWNERSHIP AND USE OF MATERIALS AND INFORMATION AND LICENSES.

                  4.1      COMPOUNDS AND [*]. All right, title and interest in
and to the Compounds and [*] shall be jointly owned by Cytokinetics and
Exelixis, shall be treated in [*] Confidential Information of [*], and each
Party shall have the right to disclose, use and exploit such Compounds and [*]
in accordance with the rights and licenses granted in this Article 4. Each Party
shall have a worldwide, [*], assignable, fully paid-up, royalty free, [*] right,
with the right to grant and authorize sublicenses subject to Section 4.1 (i) and
(ii) below, under such right, title and interest to disclose, use and exploit
the Compounds and [*], including the right to resynthesize such Compounds, for
(i) Internal Research Use, and (ii) Drug Product Use, [*]; provided, in each
case, [*] shall have the right to sell, license, sublicense, lend, lease, assign
or otherwise transfer the Compounds and/or [*] to any third party, except (a)
for contract research, contract development, contract manufacturing or
Collaboration purposes or (b) as a Drug Product. The Parties expressly
understand and agree that no rights or licenses are granted by [*] to [*] under
this Section 4.1, whether by implication, estoppel or otherwise, except as
expressly set forth in this Section 4.1. [*] shall have the right to research,
develop, make, have made, import, have imported, use, sell and offer for sale
analogs and derivatives of the Compounds without limitation, but no rights or
licenses are granted, or obligations imposed, [*] pertaining to such analogs and
derivatives. Subject to the confidentiality provisions contained herein, [*]
shall also have the right to practice and use [*] with such analogs and
derivatives.

                  4.2      LICENSE TO EXELIXIS BACKGROUND TECHNOLOGY.

                           4.2.1    COMPOUNDS. For each Compound on an Accepted
Plate and its corresponding Program Compound Information, Exelixis hereby grants
to Cytokinetics a worldwide, nonexclusive, royalty-free, fully-paid-up, [*],
sublicenseable subject to Section 4.2.1(i) and (ii) below, right and license,
under the Exelixis Background Technology to practice and use all intellectual
property rights therein with respect to such Compound and Program Compound
Information, including the right to resynthesize such Compounds, for (i)
Internal Research Use, and (ii) Drug Product Use; provided, Cytokinetics shall
not have the right to license or sublicense the Exelixis Background Technology
to any third party, except as it relates to its practice and use of the

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<PAGE>

Compounds and/or Program Compound Information (a) for contract research,
contract development, contract manufacturing or Collaboration purposes, or (b)
as a Drug Product.

                           4.2.2    ANALOGS AND DERIVATIVES OF COMPOUNDS. In
addition, Exelixis hereby grants to Cytokinetics a worldwide, nonexclusive,
royalty-free, fully-paid-up, [*], sublicenseable (as provided below), right and
license, under the Exelixis Background Technology to practice and use all
methods of synthesis developed prior to the Effective Date and/or under the
Research Program, in each case, to research, develop, make, have made, import,
have imported, use, sell and offer for sale analogs and derivatives of such
Compounds and Program Compound Information for the same uses described in
Section 4.2.1 (i) and (ii) above, except such uses, including sublicensing
rights, shall apply to such analogs and derivatives rather than such Compounds.

                  4.3      PATENTS AND PATENT APPLICATIONS.

                           4.3.1    COMPOUND PATENTS. It is anticipated that
each Party may independently file Compound Patents claiming Compounds when
utility has been established for such Compounds by or on behalf of a Party. Each
Party hereby grants to the other Party a worldwide, perpetual, irrevocable,
assignable, fully paid-up, royalty-free, non-exclusive license, (with the right
to sublicense to third parties pursuant to a Collaboration), under its Compound
Patents to practice and use any and all methods of use and compositions of
matter claims contained therein obtained on the Compound(s), including the right
to resynthesize such Compound(s), in each case, solely for Internal Research
Use. Notwithstanding the foregoing, it is understood that a patent claim of a
Compound Patent may encompass many compounds in addition to the Compound(s), and
that no license or other intellectual property right is granted to the other
Party in respect of such additional compounds encompassed by the claims,
including any methods of use or compositions of matter thereof, that are not
Compound(s).

                           4.3.2    NOVEL COMPOUNDS: INVENTORSHIP AND COMPETING
FILINGS.

                                    (a)      DESIGN CRITERIA. The JRC shall,
with respect to each Compound designed and/or synthesized under the Research
Program, mutually determine in good faith whether the chemical identity of such
Compound was designed solely by Cytokinetics, solely by Exelixis, or jointly.
After this mutual determination is made, the JRC shall document the full names
of each Party's personnel responsible for the design of such Compound in
question in a suitable database or other permanent record to which both Parties
and their counsel shall have access. The Parties acknowledge that their
determination of design under this Section 4.3.2 will be made in the absence of
any knowledge concerning the specific utility of such Compounds. Accordingly,
any determination made under this Section 4.3.2 shall be limited to design,
alone, and shall not, per se, be construed as a determination of inventorship of
such Compounds in question.

                                    (b)      INVENTORSHIP AND COMPETING FILINGS.

                                             (i)    The timing and strategy of
filing Compound Patents shall be at the sole discretion of the Party wishing to
file ("the Applicant Party"); provided both Parties agree not to file any
Compound Patent claiming one (1) or more Compounds until utility has been in

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<PAGE>

good faith reasonably established for such Compounds by or on behalf of such
Party. The Applicant Party shall be under no obligation to discuss or disclose
any portion of any Compound Patents to the other Party (the "Non-Applicant
Party"), except, and only to the extent, as may be required by law to enable the
Non-Applicant Party to perform its obligations under this Section 4.3.2. Subject
to the foregoing, in no event shall the Applicant Party be required to disclose
additional subject matter of the patent claims in such Compound Patents, such as
specific uses recited or generic structures that encompass the Compound(s)
and/or other compounds claimed. If an employee of the Non-Applicant Party is
determined to be an inventor on a claim covering a Compound within a Compound
Patent of the Applicant Party, then the Non-Applicant Party hereby assigns and
agrees to assign its rights (subject to Section 4.3.2(b)(ii) below), and shall
use its best efforts to ensure that such employee inventors assign their rights,
of inventorship and ownership in such claim to the extent such claim is
specifically directed to such Compound (but not to any other compounds covered
in such claim), obtained by virtue of holding said rights under a duty to
assign, to the Applicant Party, and to take all reasonable steps necessary, at
the Applicant Party's expense, to perfect such assignment. It is understood and
agreed that such claims on novel Compounds assigned under this Section 4.3.2
shall be subject to the licenses set forth in Section 4.3.1, including any
rights and restrictions contained therein.

                                             (ii)   For the avoidance of doubt,
it is understood by the Parties that both may file Compound Patents on the same
Compound(s) with the same or substantially the same utility, and that under this
set of circumstances, the national patent laws in each country where competing
filings are made shall be applied in and by the respective patenting authorities
to determine questions of priority and patentability and shall determine the
ownership of the competing claims. Each Party further agrees to cooperate, and
shall use [*] efforts to ensure that its employee inventors cooperate, with
the other in making any declarations, oath, assignments and the like necessary
to perfect such filings. With respect to any information disclosed by a Party to
the other Party pursuant to this Section 4.3.2, notwithstanding anything to the
contrary in this Agreement, the receiving Party acknowledges that it shall have
no right to use or disclose such information of the disclosing Party without the
disclosing Party's prior written consent.

                                    (c)      SUBSEQUENT DISCLOSURES. With
respect to any further disclosures that may be required in order to prosecute
and maintain claims already assigned under this Section 4.3.2, the assigning
Party (the "Assignor") agrees to cooperate with the Party to whom such claims
have been assigned (the "Assignee"), and to take all [*] steps necessary to
perfect such assignment, including without limitation to use [*] efforts to
ensure that each of its employee inventors on such claims cooperates with the
Assignee on such further disclosures. On a case-by case basis, the Parties shall
discuss and agree upon a mechanism by which such employee inventors of the
Assignor on such claims may communicate and cooperate directly with the
Assignee, including without limitation, having such employee inventors enter
into a separate confidentiality agreement (which covers only such further
disclosures) directly with the Assignee.

                           4.3.3    PROSECUTION OF PATENTS. Each Party shall be
solely responsible, at Its own expense and discretion, for prosecuting,
maintaining, enforcing and defending patents solely owned by such Party,
including without limitation those patent claims assigned to it by the other
Party pursuant to Section 4.3.2.

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         5.       CONFIDENTIAL INFORMATION.

                  5.1      CONFIDENTIALITY. Each Party agrees to maintain, for a
period of ten (10) years from the date of disclosure, as confidential and not
use for any purpose or disclose to any third party (except to (i) Exelixis
Third Party Suppliers under Section 2.4, (ii) third party contractors from
academic and contract research and/or development organizations authorized to
conduct activities for a Party (including its Collaboration partners) under
Article 4, and (iii) Collaboration partners, in each case, on a need to know
basis under circumstances that ensure the confidentiality thereof), all
information disclosed by one Party to the other Party under this Agreement,
whether in writing or presented, stored or maintained in or by electronic,
magnetic or other means, and marked "Confidential" at the time of such
disclosure, or if disclosed orally, confirmed in writing and marked as
"Confidential" within thirty (30) days following such oral disclosure, including
without limitation all such information relating to the business, plans and/or
technology of the Parties hereto, including, but not limited to technical
information, including inventions, discoveries, methods, plans, processes,
specifications, characteristics, raw data, equipment design, know-how, show-how,
experience and trade secrets; developmental, marketing, sales, operating and
performance information; computer programming techniques; computational
chemistry data or processes; information relating to the design of chemical
structures and compounds, synthetic protocols, analytical data and procedures,
including but not limited to, the Research Program, the Compounds and/or Program
Compound Information for drug discovery and/or parallel synthesis directed to
therapeutic, diagnostic, prophylactic, prognostic, agrochemical or agricultural
applications; and all record-bearing media containing or disclosing the
foregoing information and techniques, including written business plans, patents
and patent applications, grant applications, notes and memoranda (collectively
"Confidential Information").

                  5.2      EXCLUSIONS. Notwithstanding the foregoing, the
Parties' obligations of confidentiality shall not apply to any information
contained within the Confidential Information, to the extent such information:

                           (a)      was known to the receiving Party at the time
of receiving such information, as evidenced by its contemporaneous written
records;

                           (b)      is now, or hereafter becomes, through no act
or failure to act on the part of the receiving Party, generally known or
available in the public domain;

                           (c)      is the subject of a written permission to
disclose provided by the disclosing Party;

                           (d)      is independently developed by or for the
receiving Party without access to, or knowledge of, the disclosing Party's
Confidential Information as evidenced by its contemporaneous written record; or

                           (e)      is hereafter furnished to the receiving
Party by a third party, as a matter of right and without restriction on
disclosure.

                                      -10
<PAGE>

                  5.3      RESTRICTIONS ON USE OF CONFIDENTIAL INFORMATION.
Notwithstanding the provisions of Section 5.1 above, each Party may disclose the
other Party's Confidential Information (i) solely to the extent necessary to
exercise the rights granted, and obligations assigned, to it hereunder (provided
it uses reasonable efforts to protect such information commensurate with the
efforts used to protect its own most sensitive information of a similar nature),
(ii) as reasonably necessary to prosecute or defend litigation; in connection
with financings, securities offerings, or merger or acquisitions; to provide
information to tax or other governmental authorities, (iii) or to the extent
such disclosure is reasonably necessary to comply with applicable governmental
laws, regulations, or orders (provided that, if a Party is required to make any
such disclosure of the other Party's Confidential Information, it will, to the
extent it may legally do so, give reasonable advance notice to the latter Party
of such disclosure and will use its reasonable efforts to secure confidential
treatment of such information prior to its disclosure (whether through
protective orders or otherwise)).

                  5.4      NONDISCLOSURE OF TERMS. Each of the Parties agrees
not to disclose to any third party the terms of this Agreement without the prior
written consent of the other Party hereto, except to such Party's attorneys,
advisors, investors, potential investors or acquirers or partners and others on
a need to know basis under circumstances that reasonably ensure the
confidentiality thereof, or to the extent required by law.

         6.       PAYMENTS.

                  6.1      INITIAL PAYMENT. Cytokinetics shall pay Exelixis an
upfront fee of (i) [*] ($[*]) upon signing of the Agreement, and (ii) [*] ($[*])
upon delivery of the first [*] ([*]) Compounds hereunder (collectively, the
"Upfront Fee"), which Upfront Fee is intended to [*] the Compounds to be
delivered to Cytokinetics during the [*] of the Research Program. Exelixis shall
invoice Cytokinetics for the first payment on the Effective Date, and the second
payment upon the delivery of the first [*] ([*]) Compounds. Cytokinetics shall
pay such invoices [*] of receipt. The [*] shall be [*] of Compounds by
Cytokinetics. It is understood and agreed that Exelixis' right to receive and
retain such payment is contingent upon Exelixis' obligation to deliver to
Cytokinetics that number of Compounds (including their substantially related
Program Compound Information) that correspond to such payments.

                  6.2      PAYMENT SCHEDULE. In consideration  of Exelixis
providing Compounds to Cytokinetics, Cytokinetics shall pay Exelixis at the rate
of [*] U.S. Dollars ($[*]) per Accepted Plate, based upon a rate of [*] U.S
Dollars ($[*]) per Compound and [*] ([*]) Compounds per Plate up to a [*] of
[*] ([*]) Compounds. All Accepted Plates shall be delivered promptly to
Cytokinetics. Exelixis shall invoice Cytokinetics for each Accepted Plate at the
rate provided herein within [*] days after the first business day of each
calendar quarter.

                  6.3      DELIVERY TERMS. All deliveries shall be F.O.B.
Exelixis shipping dock at the address located at the front of this Agreement,
and Cytokinetics shall assume all shipping and

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  the Commission. Confidential treatment has been requested with respect to the
  omitted portions.

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insurance charges for delivery of such Compounds, which shall be billed directly
to Cytokinetics from the carrier, unless otherwise agreed by the Parties.

                  6.4      PAYMENT TERMS. Subject to the acceptance of Compounds
by Cytokinetics as set forth in Section 3.4.3, payments by Cytokinetics to
Exelixis shall be due within [*] upon receipt of invoice from Exelixis;
provided, it is understood and agreed that Cytokinetics shall have no obligation
to make any payments to Exelixis, until such time as the [*] is [*] of the first
[*] ([*]) of such Compounds by Cytokinetics.

         7.       REPRESENTATIONS AND WARRANTIES.

                  7.1      Each of the Parties hereby represents and warrants,
as of the Effective Date, as follows;

                           (a)      It is a corporation or entity duly organized
and validly existing under the laws of the state or other jurisdiction of its
incorporation or formation.

                           (b)      It has the full corporate power and
authority to execute and deliver this Agreement and to consummate the
transactions contemplated hereby.

                           (c)      All corporate acts and other proceedings
required to be taken to authorize such execution, delivery and consummation have
been duly and properly taken and obtained.

                           (d)      This Agreement has been duly executed and is
a legal and valid obligation binding upon such Party and enforceable in
accordance with its terms.

                           (e)      It has not previously granted, and during
the Term (as defined in Section 8.1) will not make any commitment or grant any
rights which are in conflict with the rights and licenses granted to other Party
herein.

                  7.2      Each of the Parties hereby agrees to promptly notify
the JRC of any change in its business which would be reasonably expected to
materially delay or impair its ability to perform its obligations hereunder, so
that the JRC may discuss and agree upon a reasonable resolution that addresses
any POTENTIAL harm caused to the other Party by such anticipated delay or
impairment.

         8.       TERM; TERMINATION.

                  8.1      TERM. The term of this Agreement shall commence on
the Effective Date and, unless earlier terminated as provided in this Article 8,
continue in full force and effect until [*] ([*]) years from the Effective Date,
as may be extended by Cytokinetics pursuant to Section 8.3 (the "Term").

                  8.2      [*] TERMINATION. Commencing upon the [*] of the
Effective Date, this Agreement may be terminated [*], with [*], at any time for
any reason upon ninety (90) days prior written notice [*]. Without limiting the
foregoing [*], upon any such notice of termination under this

* Certain information on this page has been omitted and filed separately with
  the Commission. Confidential treatment has been requested with respect to the
  omitted portions.

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Section 8.2, the Parties shall agree upon and issue a joint press statement
[*].

                  8.3      EXTENSION OF DELIVERY SCHEDULE OF COMPOUNDS.
Cytokinetics [*] may extend the overall timeline for design, development and
delivery of the Compounds (as summarized in Section 3.4.1-Table 1, for Years
[*]), and, concurrent with such extension, extend the Term of this Agreement up
to an additional [*], upon ninety (90) days prior written notice to Exelixis.
Notwithstanding the above, the number of Compounds to be delivered by Exelixis
to Cytokinetics in Year [*] shall be [*] ([*]) Compounds, and upon mutual
agreement of the Parties, Cytokinetics may [*] the number of Compounds to be
delivered by Exelixis in any given year, but such [*] shall not be [*] ([*])
Compounds per year.

                  8.4      TERMINATION FOR MATERIAL BREACH. Ether Party may
terminate this Agreement for any material breach of this Agreement by the other
Party, if such breach is not cured within sixty (60) days after the breaching
Party receives written notice of such breach by the nonbreaching Party. Such
termination shall be effective upon expiration of such sixty (60) day period.

                  8.5      EFFECTS OF TERMINATION.

                  8.5.1    ACCRUED RIGHTS. Termination of this Agreement shall
not affect the rights and obligations of the Parties that accrued prior to the
effective date of such termination.

                  8.5.2    CONFIDENTIAL INFORMATION. Upon request, each Party
agrees to destroy any copies of Confidential Information of the other Party
whenever the work hereunder for which they have been supplied is completed,
discontinued or otherwise terminated, other than any Confidential Information
contained within the Compounds and/or Program Compound Information, Reports
and/or Records. Notwithstanding the above, the Parties expressly agree that one
(1) complete set of Confidential Information may be retained solely for
evidentiary purposes.

                  8.5.3    MATERIALS. Upon any termination of this Agreement,
other than for uncured failure to make payments due by Cytokinetics in
accordance with Sections 6.1, 6.2, and/or 8.5.4, Exelixis shall cooperate fully
and timely with Cytokinetics regarding the transfer to Cytokinetics of
Cytokinetics' [*] Plates, Compounds (including any partial or completed
compounds paid for by Cytokinetics), templates, starting materials,
intermediates, synthons and building blocks relating to such Compounds
(including any partial or completed compounds paid for by Cytokinetics) and
necessary or useful for the synthesis thereof, Program Compound Information,
Reports and Records.

                  8.5.4    COSTS AND PAYMENTS.

                           (a)      Upon notice of any termination of this
Agreement prior to expiration of its Term, Exelixis shall stop all further work
under the Research Program, and use its best efforts to cancel any cancelable
costs. Notwithstanding anything to the contrary in this Agreement, Cytokinetics
shall have no obligation to make any payments to Exelixis for any Compounds
delivered after notice of such termination that fail to meet the QCC.

* Certain information on this page has been omitted and filed separately with
  the Commission. Confidential treatment has been requested with respect to the
  omitted portions.

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<PAGE>
                           (b)      If [*] under Section 8.2, Cytokinetics shall
pay Exelixis (i) in [*] for any compounds [*] for synthesis by the JRC [*];
provided, such compounds meet the QCC or are accepted by the JRC as Compounds
(or if the IRC is no longer in existence, by mutual agreement of the Parties),
and are delivered to Cytokinetics, with their substantially relating Program
Compound Information, within [*] ([*]) months after such submission for
synthesis by the JRC, and (ii) [*] of all actual, reasonable, documented,
non-cancelable costs incurred by Exelixis prior to the effective date of such
termination, to the extent such costs were approved by the JRC (or if incurred
after the effective date of such termination, to the extent such costs are [*]
and are necessary to synthesize and deliver such Compounds), and subject to
Exelixis using [*] to cancel all cancelable costs. Within thirty (30) days of
delivery of the last of the Compounds in accordance with this Section 8.5.4(b),
Exelixis shall provide Cytokinetics with an invoice setting forth the amount
owed for such Compounds ([*]), its actual, reasonable, documented,
non-cancelable costs incurred by Exelixis for the conduct of the Research
Program prior to the effective date of such termination, and such costs incurred
by Exelixis and [*] after the effective date of such termination and prior to
the effective date of delivery of the last of the Compounds (and to the extent
any amounts remain from any moneys previously paid by Cytokinetics to Exelixis,
the outstanding balance in such account).

                           (c)      If Exelixis terminates this Agreement
pursuant to Section 8.4 due to Cytokinetics' material breach, Cytokinetics
agrees to pay Exelixis (i) in [*] for any compounds that meet the QCC or are
accepted by JRC as Compounds, and are delivered to Cytokinetics, with their
substantially relating Program Compound Information, prior to the effective date
of termination, and (ii) [*] of all actual, reasonable, documented,
non-cancelable costs incurred by Exelixis prior to the effective date of
termination, to the extent such costs were approved by the JRC and subject to
Exelixis [*] to cancel all cancelable costs. Within thirty (30) days of any such
termination, Exelixis shall provide Cytokinetics with an invoice setting forth
the amount owed for such Compounds ([*]), and its actual, reasonable,
documented, non-cancelable costs incurred by Exelixis for the conduct of the
Research Program prior to the effective date of such termination (and to the
extent any amounts remain from any moneys previously paid by Cytokinetics to
Exelixis, the outstanding balance in such account).

                           (d)      If Cytokinetics terminates this Agreement
pursuant to Section 8.4 due to Exelixis' material breach, without limiting any
remedies Cytokinetics may have at law, Cytokinetics agrees to pay Exelixis in
[*] for any compounds that meet the QCC or are accepted by JRC as Compounds, and
are delivered to Cytokinetics, with their substantially relating Program
Compound Information, prior to the effective date of termination. Within thirty
(30) days of any such termination, Exelixis shall provide Cytokinetics with an
invoice setting forth the amount owed for such Compounds ([*]) (and to the
extent any amounts remain from any moneys previously paid by Cytokinetics to
Exelixis, the outstanding balance in such account).

                           (e)      Subject to delivery to Cytokinetics of the
materials and information listed in Section 8.5.3, and verification by
Cytokinetics of Exelixis' invoice, within

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  the Commission. Confidential treatment has been requested with respect to the
  omitted portions.

                                      -14

<PAGE>

thirty (30) days after receipt of adequate documentation therefor, the Parties
shall settle, in accordance with this Section 8.5.4, any such outstanding
amounts. If there is a balance owed to Exelixis, Cytokinetics shall make a
payment to Exelixis (and/or Exelixis may retain from moneys previously paid by
Cytokinetics) for such Compounds and, except for termination of this Agreement
due to Exelixis' material breach, such Exelixis' costs. Following settlement of
such outstanding amounts, if there is a balance remaining in Exelixis' accounts
from any moneys previously paid by Cytokinetics to Exelixis, Exelixis shall
refund such amounts to Cytokinetics.

                  8.6.     SURVIVAL. The provisions of Articles 4, 5, 7, 9, 10,
11, 12, 13, 14, 15, 16, 17, 18, 19, 20 and 21 and Sections 6.1, 8.5 and 8.6
shall survive termination or expiration of this Agreement for any reason. Upon
any termination of this Agreement, neither Party shall have any ongoing
obligation to the other Party, except as expressly provided herein.

         9.       PUBLICITY. The Parties shall issue a mutually agreed-upon
joint press release to announce the signing of this Agreement; thereafter,
Exelixis and Cytokinetics may each disclose to third parties the information
contained in such press release without the need for further approval by the
other.

         10.      PUBLIC PRESENTATIONS. The Parties acknowledge that they,
independently or jointly, may wish to make a Public Presentation of information
and data generated in the course of the Research Program. The term "Public
Presentation" shall mean the submission for publication of any manuscript,
abstract or other form of public presentation, including, without limitation,
posters, doctoral theses, slides and texts of oral presentations, and texts of
any transmission through any electronic media, e.g. any computer access system
such as the Internet, World wide Web, etc.

The Party wishing to make a Public Presentation (the "Publishing Party") shall
provide to the other Party (the "Non-Publishing Party") a complete copy of its
proposed publication at least thirty (30) days prior to the date of its intended
submission for publication, and agrees, upon request, not to submit any such
abstract or manuscript for publication until (i) the Non-Publishing Party is
given a reasonable period of time to secure patent protection for any material
in such proposed publication which it believes to be patentable, and (ii) to
remove, at the Non-Publishing Party's reasonable request, any Confidential
Information of the Non-Publishing Party and/or any [*] contained within such
proposed publication. Both Parties understand that a reasonable commercial
strategy may require delay of publication of information contained within a
Public Presentation for filing of patent applications. Neither Party shall have
the right to publish or present Confidential Information of the other Party or
any [*] in any Public Presentation without the other Party's prior written
consent. Subject to the foregoing, at the Non-Publishing Party's reasonable
request, the Publishing Party shall remove the [*]  and Non-Publishing Party's
Confidential Information from such proposed publication. The Publishing Party
agrees to provide the Non-Publishing Party with a final copy of the proposed
publication prior to its disclosure.

Nothing contained in this Article 10 is intended to grant any right or license
to either Party to commercialize or file patent applications on any information
of the Publishing Party that is included in such Public Presentation. Any
disputes between the Parties regarding delaying a Public Presentation to permit
the filing of a patent application shall be referred to the JRC.

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  the Commission. Confidential treatment has been requested with respect to the
  omitted portions.

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         11.      INDEMNIFICATION.

                  11.1     INDEMNIFICATION. Each Party agrees to be responsible
and assume liability for its own acts, gross negligence, and/or willful
misconduct, including those of its employees, Affiliates, independent
contractors and other agents, to the full extent permitted by law, and shall
indemnify and hold the other Party, and its employees, Affiliates, directors and
agents, harmless from and against any third party claims or liabilities
(including, without limitation, reasonable attorney's fees) arising from any
such acts or gross negligence, and/or willful misconduct; provided, however,
that the Party entitled to indemnification pursuant to this Article 10 shall
cooperate with the indemnifying Party in defending against any such claims or
liabilities and shall not settle any such claim without the prior consent of the
indemnifying Party, which consent shall not be unreasonably withheld.

                  11.2     PROCEDURES. A Party (the "Indemnitee") that intends
to claim indemnification under this Article 11 shall promptly notify the other
Party (the "Indemnitor") in writing of any claim, complaint, suit, proceeding or
cause of action in respect of which the Indemnitee intends to claim such
indemnification (for purposes of this Section 11.2, each a "Claim"), and the
Indemnitor shall have sole control of the defense and/or settlement thereof;
provided that the Indemnitee shall have the right to participate, at its own
expense, with counsel of its own choosing in the defense and/or settlement of
such Claim. The indemnification under this Article 11 shall not apply to amounts
paid with respect to settlement of any Claim if such settlement is effected
without the consent of the Indemnitor, which consent will not be unreasonably
withheld or delayed. The failure to deliver written notice to the Indemnitor
within a reasonable period of time after the commencement of any such claim,
suit or proceeding, if prejudicial to its ability to defend such action, shall
relieve such Indemnitor of any liability to the Indemnitee under this Article
11, but the omission to so deliver written notice to the Indemnitor shall not
relieve the Indemnitor of any liability to any Indemnitee otherwise than under
this Article 11. Without limiting the foregoing, the Indemnitee shall keep the
Indemnitor fully informed of the progress of any Claim for which it intends to
claim, indemnification under this Article 11.

         12.      FORCE MAJEURE. Except with respect to the payment of monies
due hereunder and the responsibility to maintain the confidentiality of
Confidential Information and the obligations of non-disclosure and non-use
thereof, neither Party shall be considered in default in the performance of any
obligation hereunder to the extent that the performance of such obligation is
prevented or delayed by fire, flood, explosion, strike, war, insurrection,
embargo, government requirement, civil or military authority, natural disaster
or any other event, occurrence or condition which is not caused, in whole or in
part, by that Party and which is beyond the reasonable control of that Party.

         13.      DISCLAIMER.

                  13.1     EACH PARTY ACKNOWLEDGES THAT THE COMPOUNDS AND
PROGRAM COMPOUND INFORMATION WHICH WILL BE PRODUCED PURSUANT TO THE RESEARCH
PROGRAM ARE EXPERIMENTAL AND THEIR PROPERTIES ARE NOT COMPLETELY KNOWN. EACH
PARTY SHALL BEAR FULL RESPONSIBILITY FOR SAFE HANDLING, STORAGE, TRANSFER AND
USE OF ANY COMPOUNDS AND PROGRAM COMPOUND INFORMATION IN ITS POSSESSION.

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<PAGE>

                  13.2     EACH PARTY AGREES TO ACT IN ACCORDANCE WITH ALL
IMPORT/EXPORT LAWS AND ENVIRONMENTAL AND DRUG LAWS AND REGULATIONS AND ALL OTHER
LAWS AND REGULATIONS APPLICABLE TO THE USE AND POSSESSION OF THE COMPOUNDS AND
PROGRAM COMPOUND INFORMATION.

                  13.3     EXCEPT AS EXPRESSLY SET FORTH HEREIN, COMPOUNDS AND
PROGRAM COMPOUND INFORMATION PROVIDED HEREUNDER. ARE PROVIDED "AS IS" AND
WITHOUT WARRANTY OR CONDITIONS OF ANY KIND, EXPRESS, IMPLIED, STATUTORY OR
OTHERWISE, INCLUDING WITHOUT LIMITATION ANY WARRANTY OF MERCHANTABILITY, OR
FITNESS FOR A PARTICULAR PURPOSE.

                  13.4     WITHOUT LIMITING THE PARTIES' RESPECTIVE
INDEMNIFICATION OBLIGATIONS UNDER ARTICLE 11, IN NO EVENT SHALL EITHER PARTY BE
LIABLE FOR ANY INCIDENTAL, CONSEQUENTIAL OR SPECIAL DAMAGES INCURRED BY THE
OTHER PARTY, INCLUDING LOST PROFITS OR ANTICIPATED REVENUES OR PROFITS RELATING
TO THE SAME), ARISING FROM OR RELATING TO THIS AGREEMENT OR THE SUBJECT MATTER
HEREOF, WHETHER BASED IN CONTRACT, TORT (INCLUDING WITHOUT LIMITATION
NEGLIGENCE) OR OTHERWISE, EVEN IF SUCH PARTY HAS BEEN ADVISED OF THE POSSIBILITY
OF SUCH DAMAGES. THESE LIMITATIONS SHALL APPLY NOTWITHSTANDING ANY FAILURE OF
ESSENTIAL PURPOSE OR ANY LIMITED REMEDY PROVIDED HEREIN.

         14.      GOVERNING LAW. The validity and interpretation of this
Agreement and the legal relations of the Parties under this Agreement shall be
governed by the laws of the State of California, without reference to its
conflict of laws principles.

         15.      ASSIGNMENT. This Agreement shall not be assignable by either
Party without the prior written consent of the other Party; except that Exelixis
or Cytokinetics may assign, at their discretion, the Agreement without such
consent (i) to an Affiliate, or (ii) to a third party pursuant to merger,
acquisition, consolidation, reorganization or sale of all or substantially all
of its assets to which this Agreement relates; provided that, such assignee or
transferee has agreed in writing to be bound by the terms and conditions of this
Agreement. Any attempted assignment contrary to this Article 15 shall be void.
Subject to the foregoing, this Agreement shall be binding upon and inure to the
benefit of the Parties, their successors and assigns.

         16.      HEADINGS. The headings for each article and section in this
Agreement have been inserted for convenience of reference only and are not
intended to limit or expand on the meaning of the language contained in the
particular article or section.

         17.      INDEPENDENT CONTRACTOR. For the purposes of this Agreement and
all services to be provided hereunder, each Party shall be, and shall be deemed
to be, an independent contractor and not an agent or employee of the other
Party. Neither Party shall have authority to make any statements,
representations or commitments of any kind, or take action, which shall be
binding on the other Party, except as may be explicitly provided for herein or
authorized by the other Party in writing.

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         18.      SEVERABILITY. If any one or more provisions of this Agreement
shall be found to be illegal or unenforceable in any respect, the validity,
legality and enforceability of the remaining provisions shall not in any way be
affected or impaired thereby, provided the surviving agreement materially
comports with the parties' original intent.

         19.      WAIVER. Waiver or forbearance by either Party or the failure
by either Party to claim a breach of any provision of this Agreement or exercise
any right or remedy provided by this Agreement or applicable law, shall not be
deemed to constitute a waiver with respect to any subsequent breach of any
provision hereof.

         20.      NOTICES. Any notice, payment or report required or permitted
to be given under this Agreement shall be deemed to have been sufficiently given
if mailed by first class certified or registered airmail addressed to the
Parties as follows:

              Exelixis - U.S. Postal Service:
                     Exelixis, Inc.
                     170 Harbor Way
                     P.O. Box 511
                     South San Francisco, California 94083-0511 USA
                     Attention: Vice President, Corporate Technology Development

              Exelixis - Other Mail Delivery Carrier:
                     Exelixis,Inc.
                     169 Harbor Way
                     South San Francisco, California 94080 USA
                     Attention: Vice President, Corporate Technology Development

              Cytokinetics:
                     Cytokinetics, Inc.
                     280 East Grand Avenue
                     South San Francisco, California 94080
                     Attention: Senior Vice President, Finance and Corporate
                                Development
                                Chief Financial Officer

         21.      ENTIRE AGREEMENT. This instrument contains the entire
agreement between the Parties hereto as to the subject matter hereof. The
provisions of the Confidential Disclosure Agreement, entered into on February
12, 2001, is expressly superseded and terminated hereby, and any confidential or
proprietary information disclosed thereunder shall be subject to the terms of
this Agreement. No verbal agreement or representation between the Parties hereto
either before, during or after execution of this Agreement shall affect or
modify any of the terms or obligations herein. No amendment or modification of
any term, provisions or conditions of this Agreement shall be binding or
enforceable unless in writing and signed by each of the Parties. This Agreement
may be executed in counterparts, each of which taken together shall be
considered part of the entire document.

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<PAGE>

The undersigned represent that they are duly authorized to execute this
Agreement.

CYTOKINETICS, INC.                             EXELIXIS, INC.

BY: /s/ Robert I. Blum                         By: /s/ Glen Y. Sato
    -------------------------                      ----------------------------

Name: Robert I. Blum                           Name: Glen Y. Sato

Title: ______________________                  Title: CFO and VP, Legal Affairs

Date: 12/28/01                                 Date: 12/28/01

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                                   APPENDIX A

                                RESEARCH PROGRAM

1) LIBRARY SCOPE & SIZE;

A library of [*] compounds based on [*] will be designed jointly by Cytokinetics
and Exelixis and subsequently synthesized by Exelixis.

2) LIBRARY CONSTRUCTION:

[*] compounds will be derived from [*] libraries of [*] compounds. Each of the
[*] libraries will be derived from [*] of [*] and a [*] of [*] per [*] (each, a
"Library"). The details and identity of [*] component for the [*] will be
determined by the JRC. Approximately [*] of each compound will be prepared and
quality controlled by [*]. [*]. For [*] compounds per plate, a [*] of [*] per
Plate will be transferred to Cytokinetics (that is, [*]). Following delivery of
the [*] Plate within a Library, Exelixis shall deliver to Cytokinetics a [*] of
[*] of each [*] used in such Library. Cytokinetics shall own all right, title
and interest in such delivered [*], and shall have the right to use and exploit
such [*] without limitation or obligation to account to Exelixis to the extent
allowed under Section 4 of the Agreement.

3) EXELIXIS COMPOUND PLATE FORMAT:

Exelixis formats screening plates in a [*] plate format with [*], i.e., a total
of [*] compounds per plate.

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  the Commission. Confidential treatment has been requested with respect to the
  omitted portions.

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                                   APPENDIX B

                            QUALITY CONTROL CRITERIA

[*]

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  the Commission. Confidential treatment has been requested with respect to the
  omitted portions.


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[*]

* Certain information on this page has been omitted and filed separately with
  the Commission. Confidential treatment has been requested with respect to the
  omitted portions.


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