<PAGE>

                                                                   Exhibit 10.38

                                 PROMISSORY NOTE

South San Francisco, California                                      $200,000.00
November 12, 2001

FOR VALUE RECEIVED, the undersigned James H. Sabry ("EMPLOYEE") and Sandra J.
Spence, (collectively, "BORROWER") hereby promises to pay to the order of
Cytokinetics, Inc., a Delaware corporation ("LENDER" also known as
"Cytokinetics") at 280 East Grand Avenue, South San Francisco, California (or at
such other address as the holder of this NOTE may designate by notice to
BORROWER), in lawful money of the United States of America, the sum of Two
Hundred Thousand Dollars ($200,000.00), as set forth below:

     1.     Definitions.

            a.    "CODE" shall mean the Internal Revenue Code of 1986, as
                  amended.

            b.    "APPLICABLE FEDERAL RATE" shall mean the monthly long-term
                  applicable Federal or other rate (as defined in the CODE) as
                  the date of the occurrence of this NOTE.

            c.    "DUE DATE" shall mean the earliest of any of the following:

                      i.    thirty (30) days after TERMINATION OF EMPLOYMENT of
                            EMPLOYEE; or

                      ii.   November 12, 2010, provided that if BORROWER is
                            unable to repay this NOTE at such time, LENDER in
                            its discretion shall consider extending the DUE
                            DATE.

            d.    "TERMINATION OF EMPLOYMENT" shall mean the voluntary or
                  involuntary termination of EMPLOYEE'S employment relationship
                  with LENDER for any reason or no reason, with or without
                  cause.

     2.     Payments.

            a.    Interest on the unpaid principal balance of this NOTE shall
                  accrue at the APPLICABLE FEDERAL RATE, compounded monthly,
                  commencing on the date hereof.

            b.    No payment of principal or interest shall be due and payable
                  until the DUE DATE, at which time all accrued interest on the
                  principal balance of this NOTE shall be due and payable.

            c.    All payments shall be applied first against accrued interest,
                  and secondly against principal.

                                                                               1
<PAGE>

     3.     Prepayment.

            BORROWER may prepay all or any portion of this NOTE and the accrued
            interest without penalty or acceleration of the DUE DATE of this
            NOTE.

     4.     Unsecured Note.

            This NOTE is unsecured.

     5.     Collection Costs Borne by BORROWER.

            In the event of any failure on the part of BORROWER to make any
            payment when the same is due, LENDER shall be entitled to recover
            from BORROWER all costs of effecting collection of the same,
            including reasonable attorneys' fees. Unpaid principal and interest
            subject to collection shall bear interest at the maximum rate
            allowed under California law for nonexempt lenders.

     6.     Termination.

            The obligation of BORROWER hereunder shall terminate upon the
            indefeasible payment in full by BORROWER of all of its obligations
            evidenced by this NOTE.

     7.     Forgiveness of NOTE and/or Accrued Interest.

            a.    In the event EMPLOYEE remains an employee in good standing of
                  LENDER, as determined in LENDER'S sole discretion, on the
                  fifth (5th) anniversary date of this NOTE, one quarter (1/4)
                  of the then outstanding principal balance of this NOTE shall
                  be forgiven on such date. Thereafter, in the event EMPLOYEE
                  remains an employee in good standing of LENDER, as determined
                  in LENDER'S sole discretion, on each succeeding anniversary
                  date of this NOTE through and including the eighth (8th)
                  anniversary date hereof, one quarter (1/4) of the then
                  outstanding principal balance of this NOTE shall be forgiven
                  on each such date.

            b.    In the event EMPLOYEE remains an employee in good standing of
                  LENDER, as determined in LENDER'S sole discretion, on each
                  anniversary date of this NOTE, all accrued interest shall be
                  forgiven on such date.

            c.    In the event that EMPLOYEE dies or becomes permanently
                  disabled, any outstanding principal balance of this NOTE and
                  all accrued interest shall be forgiven on such date.

            d.    In the event of any such forgiveness of principal and/or
                  interest, BORROWER shall be responsible for all taxes related
                  thereto.

                                       2
<PAGE>

     8.     Governing Law.

            This NOTE shall be governed by and construed in accordance with the
            internal laws of the State of California. BORROWER consents to
            personal jurisdiction in any court in San Mateo County, California.

     9.     Successors.

            This NOTE shall be binding upon and share inure to the benefit of
            the parties hereto and their respective representatives, heirs,
            administrators, successors and assigns.

Effective as of the date set forth above.

BORROWER:

/s/ James H. Sabry
-----------------------
James H. Sabry

/s/ Sandra J. Spence
-----------------------
Sandra J. Spence

ACCEPTED AND ACKNOWLEDGED:

LENDER

CYTOKINETICS, INC., a Delaware corporation

By:    /s/ Robert I. Blum
       --------------------------------
Name:  Robert I. Blum
Title: Senior Vice President,
       Corporate Development & Finance,
       Chief Financial Officer

                                        3
<PAGE>

EXHIBIT C

                                      LOAN

The Company is offering you a loan for up to $200,000. The loan will be interest
free and will also be forgivable over a nine-year period of time during your
employment with the Company.

At the end of the fifth year one-quarter of the loan is forgiven; at the end of
the sixth, seventh and eight year one-quarter of the loan on each of those years
will be forgiven. Should you decide to voluntarily terminate your position with
the Company prior to the end of your fifth year of employment at Cytokinetics,
you will be responsible for reimbursing the Company for your full loan upon
departure from the Company. If you voluntarily leave anytime during the sixth,
seventh or eighth year, the amount of the loan minus the forgiven portion is due
to the Company upon your departure.

You are required to pay imputed taxes as regular income on the interest rate
(set at Prime Rate) of the interest "free" loan. At the end of the fifth, sixth,
seventh and eighth year you will be required to pay taxes only on the forgivable
portion of the loan (one-quarter of the loan each year).