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                                                                   Exhibit 10.39

                           CYTOKINETICS, INCORPORATED

                              CASH BONUS AGREEMENT

         This Cash Bonus Agreement (the "Agreement") is entered into effective
as of SEPTEMBER 1, 2002(the "Effective Date"), by and between Cytokinetics,
Incorporated, a Delaware corporation (the "Company"), and Robert I. Blum (the
"Employee").

         1.       Cash Bonus. The Company hereby agrees to pay Employee cash
bonuses in the amount of: (i) $7,000, less applicable withholding taxes, on June
30, 2003, (ii) $7,000, less applicable withholding taxes, on June 30, 2004,
(iii) $27,000, less applicable withholding taxes, on June 30, 2005, (iv) $25,000
less applicable withholding taxes, on June 30, 2006, (v) $24,000, less
applicable withholding taxes, on June 30, 2007 and (vi) $3,000, less applicable
withholding taxes, on June 30, 2008 (collectively, the "Cash Bonus"), provided
that Employee remains an employee in good standing of the Company, as determined
in the Company's sole discretion, on each such date.

         2.       No Right To Continued Employment. Nothing contained herein
shall be construed to confer on Employee any right to continued employment with
the Company. The Company or Employee may terminate the employment relationship
of Employee with the Company for any reason or no reason, with or without cause,
and after such termination Employee shall not have any right to receive any
further payments of Cash Bonus remaining unpaid at such time.

         3.       Taxes. Employee shall be responsible for all taxes related to
the Cash Bonus.

         4.       Integration; No Assignment. This Agreement represents the
entire agreement and understanding between the parties as to the Cash Bonus, and
supersedes all prior or contemporaneous agreements whether written or oral;
provided, however, that this Agreement is meant to be in addition to any other
compensation arrangements Employee may have with the Company. No waiver,
alteration, or modification of any of the provisions of this Agreement shall be
binding unless in writing and signed by the parties hereto or their duly
authorized representatives. Neither this Agreement nor any rights of Employee
hereunder may be assigned or transferred by Employee.

         5.       Applicable Law. This Agreement shall be governed by and
construed in accordance with the internal substantive laws, but not the choice
of law rules, of the State of California.

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         IN WITNESS WHEREOF, each of the parties has executed this Agreement, in
the case of the Company by its duly authorized officer, as of the day and year
first above written.

                                       CYTOKINETICS, INCORPORATED

                                       By: /s/ James Sabry
                                           -------------------------------------
                                       Title:
                                              ----------------------------------
                                       EMPLOYEE

                                                  /s/ Robert Blum
                                       -----------------------------------------
                                       Signature

                                                  Robert I. Blum
                                       -----------------------------------------
                                       Name

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