Document:

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                                                                     Exhibit 4.7

                            MASTER SECURITY AGREEMENT
                    dated as of FEBRUARY 2, 2001 ("AGREEMENT")

         THIS AGREEMENT is between GENERAL ELECTRIC CAPITAL CORPORATION
(together with its successors and assigns, if any, "SECURED PARTY") and
CYTOKINETICS, INCORPORATED ("DEBTOR"). Secured Party has an office at 401
Merritt 7 2nd Floor, Norwalk, CT 06856. Debtor is a corporation organized and
existing under the laws of the state of Delaware. Debtor's mailing address and
chief place of business is 280 East Grand Avenue, Suite 2, South San Francisco,
CA 9408O.

1.       CREATION OF SECURITY INTEREST.

         Debtor grants to Secured Party, its successors and assigns, a security
interest in and against all property listed on any collateral schedule now or in
the future annexed to or made a part of this Agreement ( "COLLATERAL SCHEDULE"),
and in and against all additions, attachments, accessories and accessions to
such property, all substitutions, replacements or exchanges therefor, and all
insurance and/or other proceeds thereof (all such property is individually and
collectively called the "COLLATERAL"). This security interest is given to secure
the payment and performance of all debts, obligations and liabilities of any
kind whatsoever of Debtor to Secured Party, now existing or arising in the
future, including but not limited to the payment and performance of certain
Promissory Notes from time to time identified on any Collateral Schedule
(collectively "NOTES" and each a "NOTE"), and any renewals, extensions and
modifications of such debts, obligations and liabilities (such Notes, debts,
obligations and liabilities are called the "INDEBTEDNESS"). Notwithstanding
anything to the contrary contained in this Agreement, to the extent that Secured
Party asserts a purchase money security interest in any items of Collateral (
"PMSI COLLATERAL"): (i) the PMSI COLLATERAL shall secure only that portion of
the Indebtedness which has been advanced by Secured Party to enable Debtor to
purchase, or acquire rights in or the use of such PMSI Collateral (the "PMSI
INDEBTEDNESS"), and (ii) no other Collateral shall secure the PMSI Indebtedness.

2.       REPRESENTATIONS, WARRANTIES AND COVENANTS OF DEBTOR.

         Debtor represents, warrants and covenants as of the date of this
Agreement and as of the date of each Collateral Schedule that:

         (a) Debtor is, and will remain, duly organized, existing and in good
standing under the laws of the State set forth in the preamble of this
Agreement, has its chief executive offices at the location specified in the
preamble, and is, and will remain, duly qualified and licensed in every
jurisdiction wherever necessary to carry on its business and operations;

         (b) Debtor has adequate power and capacity to enter into, and to
perform its obligations under this Agreement, each Note and any other documents
evidencing, or given in connection with, any of the Indebtedness (all of the
foregoing are called the "DEBT DOCUMENTS");

         (c) This Agreement and the other Debt Documents have been duly
authorized, executed and delivered by Debtor and constitute legal, valid and
binding agreements enforceable in accordance with their terms, except to the
extent that the enforcement of remedies may be limited under applicable
bankruptcy and insolvency laws;

         (d) No approval, consent or withholding of objections is required from
any governmental authority or instrumentality with respect to the entry into, or
performance by Debtor of any of the Debt Documents, except any already obtained;

         (e) The entry into, and performance by, Debtor of the Debt Documents
will not (i) violate any of the organizational documents of Debtor or any
judgment, order, law or regulation applicable to Debtor, or (ii) result in any
breach of or constitute a default under any contract to which Debtor is a party,
or result in the creation of any lien, claim or encumbrance on any of Debtor's
property (except for liens in favor of Secured Party) pursuant to any indenture,
mortgage, deed of trust, bank loan, credit agreement, or other agreement or
instrument to which Debtor is a party;

         (f) There are no suits or proceedings pending in court or before any
commission, board or other administrative agency against or affecting Debtor
which could, in the aggregate, have a material adverse effect on Debtor, its
business or operations, or its ability to perform its obligations under the Debt
Documents, nor does Debtor have reason to believe that any such suits or
proceedings are threatened;

         (g) All financial statements delivered to Secured Party in connection
with the Indebtedness have been prepared in accordance with generally accepted
accounting principles, and since the date of the most recent financial
statement, there has been no material adverse change in Debtors financial
condition;

         (h) The Collateral is not, and will not be, used by Debtor for
personal, family or household purposes;

         (i) The Collateral is, and will remain, in good condition and repair
and Debtor will not be negligent in its care and use;

         (j) Debtor is, and will remain, the sole and lawful owner, and in
possession of the Collateral, and has the sole right and lawful authority to
grant the security interest described in this Agreement; and

         (k) The Collateral is, and will remain, free and clear of all liens,
claims and encumbrances of any kind whatsoever, except for (i) liens in favor of
Secured Party, (ii) liens for taxes not yet due or for taxes being contested in
good faith and which do not involve, in the judgment of Secured Party, any risk
of the sale, forfeiture or loss of any of the Collateral, and (iii) inchoate
materialmen's, mechanic's, repairmen's and similar liens arising by operation of
law in the normal course of business for amounts which are not delinquent (all
of such liens are called "PERMITTED LIENS").

3.       COLLATERAL.

         (a) Until the declaration of any default, Debtor shall remain in
possession of the Collateral; except that Secured Party shall have the right to
possess (i) any chattel paper or instrument that constitutes a part of the
Collateral, and (ii) any other Collateral in which Secured Party's security
interest may be perfected only by possession. Secured Party may inspect any of
the Collateral during normal business hours after giving Debtor reasonable prior
notice. If Secured Party asks, Debtor will promptly notify Secured Party in
writing of the location of any Collateral.

<PAGE>

         (b) Debtor shall (i) use the Collateral only in its trade or business,
(ii) maintain all of the Collateral in good operating order and repair, normal
wear and tear excepted, (iii) use and maintain the Collateral only in compliance
with manufacturers recommendations and all applicable laws, and (iv) keep all of
the Collateral free and clear of all liens, claims and encumbrances (except for
Permitted Liens).

         (c) Debtor shall not, without the prior written consent of Secured
Party, (i) part with possession of any of the Collateral (except to Secured
Party or for maintenance and repair), (ii) remove any of the Collateral from the
continental United States, or (iii) sell, rent, lease, mortgage, grant a
security interest in or otherwise transfer or encumber (except for Permitted
Liens) any of the Collateral.

         (d) Debtor shall pay promptly when due all taxes, license fees,
assessments and public and private charges levied or assessed on any of the
Collateral, on its use, or on this Agreement or any of the other Debt Documents.
At its option, Secured Party may discharge taxes, liens, security interests or
other encumbrances at any time levied or placed on the Collateral and may pay
for the maintenance, insurance and preservation of the Collateral and effect
compliance with the terms of this Agreement or any of the other Debt Documents.
Debtor agrees to reimburse Secured Party, on demand, all costs and expenses
incurred by Secured Party in connection with such payment or performance and
agrees that such reimbursement obligation shall constitute Indebtedness.

         (e) Debtor shall, at all times, keep accurate and complete records of
the Collateral, and Secured Party shall have the right to inspect and make
copies of all of Debtor's books and records relating to the Collateral during
normal business hours, after giving Debtor reasonable prior notice.

         (f) Debtor agrees and acknowledges that any third person who may at any
time possess all or any portion of the Collateral shall be deemed to hold, and
shall hold, the Collateral as the agent of, and as pledge holder for, Secured
Parry. Secured Party may at any time give notice to any third person described
in the preceding sentence that such third person is holding the Collateral as
the agent of, and as pledge holder for, the Secured Party.

4.       INSURANCE.

         (a) Debtor shall at all times bear the entire risk of any loss, theft,
damage to, or destruction of, any of the Collateral from any cause whatsoever.

         (b) Debtor agrees to keep the Collateral insured against loss or damage
by fire and extended coverage perils, theft, burglary, and for any or all
Collateral which are vehicles, for risk of loss by collision, and if requested
by Secured Party, against such other risks as Secured Party may reasonably
require. The insurance coverage shall be in an amount no less than the full
replacement value of the Collateral, and deductible amounts, insurers and
policies shall be acceptable to Secured Party. Debtor shall deliver to Secured
Party policies or certificates of insurance evidencing such coverage. Each
policy shall name Secured Party as a loss payee, shall provide for coverage to
Secured Party regardless of the breach by Debtor of any warranty or
representation made therein, shall not be subject to co-insurance, and shall
provide that coverage may not be canceled or altered by the insurer except upon
thirty (30) days prior written notice to Secured Party. Debtor appoints Secured
Party as its attorney-in-fact to make proof of loss, claim for insurance and
adjustments with insurers, and to receive payment of and execute or endorse all
documents, checks or drafts in connection with insurance payments. Secured Party
shall not act as Debtors attorney-in-fact unless Debtor is in default. Proceeds
of insurance shall be applied, at the option of Secured Party, to repair or
replace the Collateral or to reduce any of the Indebtedness.

5.       REPORTS.

         (a) Debtor shall promptly notify Secured Party of (i) any change in the
name of Debtor, (ii) any relocation of its chief executive offices, (iii) any
relocation of any of the Collateral, (iv) any of the Collateral being lost,
stolen, missing, destroyed, materially damaged or worn out, or (v) any lien,
claim or encumbrance other than Permitted Liens attaching to or being made
against any of the Collateral.

         (b) Debtor will deliver to Secured Party Debtors complete financial
statements, certified by a recognized firm of certified public accountants,
within ninety (90) days of the close of each fiscal year of Debtor. If Secured
Party requests, Debtor will deliver to Secured Party copies of Debtors quarterly
financial reports certified by Debtors chief financial officer, within ninety
(90) days after the close of each of Debtors fiscal quarter. Debtor will deliver
to Secured Party copies of all Forms 10-K and 10-Q, if any, within 30 days after
the dates on which they are filed with the Securities and Exchange Commission.

6.       FURTHER ASSURANCES.

         (a) Debtor shall, upon request of Secured Party, furnish to Secured
Party such further information, execute and deliver to Secured Party such
documents and instruments (including, without limitation, Uniform Commercial
Code financing statements) and shall do such other acts and things as Secured
Party may at any time reasonably request relating to the perfection or
protection of the security interest created by this Agreement or for the purpose
of carrying out the intent of this Agreement. Without limiting the foregoing,
Debtor shall cooperate and do all acts deemed necessary or advisable by Secured
Party to continue in Secured Party a perfected first security interest in the
Collateral, and shall obtain and furnish to Secured Party any subordinations,
releases, landlord, lessor, or mortgagee waivers, and similar documents as may
be from time to time requested by, and in form and substance satisfactory to,
Secured Party.

         (b) Debtor irrevocably grants to Secured Party the power to sign
Debtor's name and generally to act on behalf of Debtor to execute and file
applications for title, transfers of title, financing statements, notices of
lien and other documents pertaining to any or all of the Collateral; this power
is coupled with Secured Party's interest in the Collateral. Debtor shall, if any
certificate of title be required or permitted by law for any of the Collateral,
obtain and promptly deliver to Secured Party such certificate showing the lien
of this Agreement with respect to the Collateral.

         (c) Debtor shall indemnify and defend the Secured Party, its successors
and assigns, and their respective directors, officers and employees, from and
against all claims, actions and suits (including, without limitation, related
attorneys' fees) of any kind whatsoever arising, directly or indirectly, in
connection with any of the Collateral.

7.       DEFAULT AND REMEDIES.

         (a) Debtor shall be in default under this Agreement and each of the
other Debt Documents if:

                  (i) Debtor breaches its obligation to pay when due any
installment or other amount due or coming due under any of the Debt Documents

                  (ii) Debtor, without the prior written consent of Secured
Party, attempts to or does sell, rent, lease, mortgage, grant a security
interest in, or

<PAGE>
otherwise transfer or encumber (except for Permitted Liens) any of the
Collateral;

                  (iii) Debtor breaches any of its insurance obligations under
Section 4;

                  (iv) Debtor breaches any of its other obligations under any of
the Debt Documents and fails to cure that breach within thirty (30) days after
written notice from Secured Party;

                  (v) Any warranty, representation or statement made by Debtor
in any of the Debt Documents or otherwise in connection with any of the
Indebtedness shall be false or misleading in any material respect;

                  (vi) Any of the Collateral is subjected to attachment,
execution, levy, seizure or confiscation in any legal proceeding or otherwise,
or if any legal or administrative proceeding is commenced against Debtor or any
of the Collateral, which in the good faith judgment of Secured Party subjects
any of the Collateral to a material risk of attachment, execution, levy, seizure
or confiscation and no bond is posted or protective order obtained to negate
such risk;

                  (vii) Debtor breaches or is in default under any other
agreement between Debtor and Secured Party;

                  (viii) Debtor or any guarantor or other obligor for any of the
Indebtedness (collectively "GUARANTOR") dissolves, terminates its existence,
becomes insolvent or ceases to do business as a going concern;

                  (ix) If Debtor or any Guarantor is a natural person, Debtor or
any such Guarantor dies or becomes incompetent;

                  (x) A receiver is appointed for all or of any part of the
property of Debtor or any Guarantor, or Debtor or any Guarantor makes any
assignment for the benefit of creditors; or

                  (xi) Debtor or any Guarantor files a petition under any
bankruptcy, insolvency or similar law, or any such petition is filed against
Debtor or any Guarantor and is not dismissed within forty-five (45) days

         (b) If Debtor is in default, the Secured Party, at its option, may
declare any or all of the Indebtedness to be immediately due and payable,
without demand or notice to Debtor or any Guarantor. The accelerated obligations
and liabilities shall bear interest (both before and after any judgment) until
paid in full at the lower of eighteen percent (18%) per annum or the maximum
rate not prohibited by applicable law.

         (c) After default, Secured Party shall have all of the rights and
remedies of a Secured Party under the Uniform Commercial Code, and under any
other applicable law. Without limiting the foregoing, Secured Party shall have
the right to (i) notify any account debtor of Debtor or any obligor on any
instrument which constitutes part of the Collateral to make payment to the
Secured Party, (ii) with or without legal process, enter any premises where the
Collateral may be and take possession of and remove the Collateral from the
premises or store it on the premises, (iii) sell the Collateral at public or
private sale, in whole or in part, and have the right to bid and purchase at
said sale, or (iv) lease or otherwise dispose of all or part of the Collateral,
applying proceeds from such disposition to the obligations then in default. If
requested by Secured Party, Debtor shall promptly assemble the Collateral and
make it available to Secured Party at a place to be designated by Secured Party
which is reasonably convenient to both parties. Secured Party may also render
any or all of the Collateral unusable at the Debtor's premises and may dispose
of such Collateral on such premises without liability for rent or costs. Any
notice that Secured Party is required to give to Debtor under the Uniform
Commercial Code of the time and place of any public sale or the time after which
any private sale or other intended disposition of the Collateral is to be made
shall be deemed to constitute reasonable notice if such notice is given to the
last known address of Debtor at least five (5) days prior to such action,

         (d) Proceeds from any sale or lease or other disposition shall be
applied: first, to all costs of repossession, storage, and disposition including
without limitation attorneys', appraisers', and auctioneers' fees; second, to
discharge the obligations then in default; third, to discharge any other
Indebtedness of Debtor to Secured Party, whether as obligor, endorser,
guarantor, surety or indemnitor; fourth, to expenses incurred in paying or
settling liens and claims against the Collateral; and lastly, to Debtor, if
there exists any surplus. Debtor shall remain fully liable for any deficiency.

         (e) Debtor agrees to pay all reasonable attorneys' fees and other costs
incurred by Secured Part)' in connection with the enforcement, assertion,
defense or preservation of Secured Party's rights and remedies under this
Agreement, or if prohibited by law, such lesser sum as may be permitted. Debtor
further agrees that such fees and costs shall constitute Indebtedness.

         (f) Secured Party's rights and remedies under this Agreement or
otherwise arising are cumulative and may be exercised singularly or
concurrently. Neither the failure nor any delay on the part of the Secured Party
to exercise any right, power or privilege under this Agreement shall operate as
a waiver, nor shall any single or partial exercise of any right, power or
privilege preclude any other or further exercise of that or any other right,
power or privilege. SECURED PARTY SHALL NOT BE DEEMED TO HAVE WAIVED ANY OF ITS
RIGHTS UNDER THIS AGREEMENT OR UNDER ANY OTHER AGREEMENT, INSTRUMENT OR PAPER
SIGNED BY DEBTOR UNLESS SUCH WAIVER IS EXPRESSED IN WRITING AND SIGNED BY
SECURED PARTY. A waiver on any one occasion shall not be construed as a bar to
or waiver of any right or remedy on any future occasion.

         (g) DEBTOR AND SECURED PARTY UNCONDITIONALLY WAIVE THEIR RIGHTS TO A
JURY TRIAL OF ANY CLAIM OR CAUSE OF ACTION BASED UPON OR ARISING OUT OF THIS
AGREEMENT, ANY OF THE OTHER DEBT DOCUMENTS, ANY OF THE INDEBTEDNESS SECURED
HEREBY, ANY DEALINGS BETWEEN DEBTOR AND SECURED PARTY RELATING TO THE SUBJECT
MATTER OF THIS TRANSACTION OR ANY RELATED TRANSACTIONS, AND/OR THE RELATIONSHIP
THAT IS BEING ESTABLISHED BETWEEN DEBTOR AND SECURED PARTY. THE SCOPE OF THIS
WAIVER IS INTENDED TO BE ALL ENCOMPASSING OF ANY AND ALL DISPUTES THAT MAY BE
FILED IN ANY COURT. THIS WAIVER IS IRREVOCABLE. THIS WAIVER MAY NOT BE MODIFIED
EITHER ORALLY OR IN WRITING. THE WAIVER ALSO SHALL APPLY TO ANY SUBSEQUENT
AMENDMENTS, RENEWALS, SUPPLEMENTS OR MODIFICATIONS TO THIS AGREEMENT, ANY OTHER
DEBT DOCUMENTS, OR TO ANY OTHER DOCUMENTS OR AGREEMENTS RELATING TO THIS
TRANSACTION OR ANY RELATED TRANSACTION. THIS AGREEMENT MAY BE FILED AS A WRITTEN
CONSENT TO A TRIAL BY THE COURT.

8.       MISCELLANEOUS.

         (a) This Agreement, any Note and/or any of the other Debt Documents may
be assigned, in whole or in part, by Secured Party without notice to Debtor, and
Debtor agrees not to assert against any such assignee, or assignee's assigns,
any defense, set-off, recoupment claim or counterclaim which Debtor has or may
at any time have against Secured Party for any reason whatsoever. Debtor agrees
that if Debtor receives written notice of an assignment from Secured Party,
Debtor will pay all amounts payable under any assigned Debt Documents to such
assignee or as instructed by Secured Party. Debtor also agrees to

<PAGE>

confirm in writing receipt of the notice of assignment as may be reasonably
requested by assignee.

         (b) All notices to be given in connection with this Agreement shall be
in writing, shall be addressed to the parties at their respective addresses set
forth in this Agreement (unless and until a different address may be specified
in a written notice to the other party), and shall be deemed given (i) on the
date of receipt if delivered in hand or by facsimile transmission, (ii) on the
next business day after being sent by express mail, and (iii) on the fourth
business day after being sent by regular, registered or certified mail. As used
herein, the term "business day" shall mean and include any day other than
Saturdays, Sundays, or other days on which commercial banks in New York, New
York are required or authorized to be closed.

         (c) Secured Party may correct patent errors and fill in all blanks in
this Agreement or in any Collateral Schedule consistent with the agreement of
the parties.

         (d) Time is of the essence of this Agreement. This Agreement shall be
binding, jointly and severally, upon all parties described as the "Debtor" and
their respective heirs, executors, representatives, successors and assigns, and
shall inure to the benefit of Secured Party, its successors and assigns.

         (e) This Agreement and its Collateral Schedules constitute the entire
agreement between the parties with respect to the subject matter of this
Agreement and supersede all prior understandings (whether written, verbal or
implied) with respect to such subject matter. THIS AGREEMENT AND ITS COLLATERAL
SCHEDULES SHALL NOT BE CHANGED OR TERMINATED ORALLY OR BY COURSE OF CONDUCT, BUT
ONLY BY A WRITING SIGNED BY BOTH PARTIES. Section headings contained in this
Agreement have been included for convenience only, and shall not affect the
construction or interpretation of this Agreement.

         (f) This Agreement shall continue in full force and effect until all of
the Indebtedness has been indefeasibly paid in full to Secured Party. The
surrender, upon payment or otherwise, of any Note or any of the other documents
evidencing any of the Indebtedness shall not affect the right of Secured Party
to retain the Collateral for such other Indebtedness as may then exist or as it
may be reasonably contemplated will exist in the future. This Agreement shall
automatically be reinstated if Secured Party is ever required to return or
restore the payment of all or any portion of the Indebtedness (all as though
such payment had never been made).

         (g) THIS AGREEMENT AND THE RIGHTS AND OBLIGATIONS OF THE PARTIES
HEREUNDER SHALL IN ALL RESPECTS BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH,
THE INTERNAL LAWS OF THE STATE OF CONNECTICUT (WITHOUT REGARD TO THE CONFLICT OF
LAWS PRINCIPLES OF SUCH STATE), INCLUDING ALL MATTERS OF CONSTRUCTION, VALIDITY
AND PERFORMANCE, REGARDLESS OF THE LOCATION OF THE EQUIPMENT.

         IN WITNESS WHEREOF, Debtor and Secured Party, intending to be legally
bound hereby, have duly executed this Agreement in one or more counterparts,
each of which shall be deemed to be an original, as of the day and year first
aforesaid.

SECURED PARTY:                             DEBTOR:

GENERAL ELECTRIC CAPITAL CORPORATION       CYTOKINETICS, INCORPORATED

By: ________________________________       By: /s/ James Sabry
                                               ---------------------------------

Name: THOMAS ANNINO                        Name:

Title: _____________________________       Title: _____________________________

GECC:

By: /s/ John Edel
    ----------------------------------

Name: John Edel
      --------------------------------

Title: SVP
       -------------------------------
<PAGE>

                  CROSS-COLLATERAL AND CROSS-DEFAULT AGREEMENT

General Electric Capital Corporation
401 Merritt 72nd Floor
Norwalk, CT 06856

Gentlemen:

         You (and/or your successors or assigns, "you") have entered into or
purchased one or more conditional sale contracts, lease agreements, chattel
mortgages, security agreements, notes and other choses in action (herein
designated "Accounts") arising from the bona fide sale or lease to us, by
various vendors or lessors, of equipment and inventory (herein designated
"Collateral") and/or you have made direct loans to or otherwise extended credit
to us evidenced by Accounts creating security interests in Collateral.

         In order to induce you to extend our time of payment on one or more
Accounts and/or to make additional loans to us and/or to purchase additional
Accounts and/or to lease us additional equipment, and in consideration of you so
doing, and for other good and valuable consideration, the receipt of which we
hereby acknowledge, we agree as follows:

         All presently existing and hereafter acquired Collateral in which you
have or shall have a security interest shall secure the payment and performance
of all of our liabilities and obligations to you of every kind and character,
whether joint or several, direct or indirect, absolute or contingent, due or to
become due, and whether under presently existing or hereafter created Accounts
or agreements, or otherwise.

         We further agree that your security interest in the property covered by
any Account now held or hereafter acquired by you shall not be terminated in
whole or in part until and unless all indebtedness of every kind, due or to
become due, owed by us to you is fully paid and satisfied and the terms of every
Account have been fully performed by us. It is further agreed that you are to
retain your security interest in all property covered by all Accounts held or
acquired by you, as security for payment and performance under each such
Account, notwithstanding the fact that one or more of such Accounts may become
fully paid.

         This instrument is intended to create cross-default and cross-security
between and among all the within described Accounts now owned or hereafter
acquired by you.

         A default under any Account or agreement shall be deemed to be a
default under all other Accounts and agreements. A default shall result if we
fail to pay any sum when due on any Account or agreement, or if we breach any of
the other terms and conditions thereof, or if we become insolvent, cease to do
business as a going concern, make an assignment for the benefit of creditors, or
if a petition for a receiver or in bankruptcy is filed by or against us, or if
any of our property is seized, attached or levied upon. Upon our default any or
all Accounts and agreements shall, at your option, become immediately due and
payable without notice or demand to us or any other party obligated thereon, and
you shall have and may exercise any and all rights and remedies of a secured
party under the Uniform Commercial Code as enacted in the applicable
jurisdiction and as otherwise granted to you under any Account or other
agreement. We hereby waive, to the maximum extent permitted by law, notices of
default, notices of repossession and sale or other disposition of collateral,
and all other notices, and in the event any such notice cannot be waived, we
agree that if such notice is mailed to us postage prepaid at the address shown
below at least five (5) days prior to the exercise by you of any of your rights
or remedies, such notice shall be deemed to be reasonable and shall fully
satisfy any requirement for giving notice.

         All rights granted to you hereunder shall be cumulative and not
alternative, shall be in addition to and shall in no manner impair or affect
your rights and remedies under any existing Account, agreement, statute or rule
of law, and remedies under any existing Account, agreement, statute or rule of
law.

         This agreement may not be varied or altered nor its provisions waived
except by your duly executed written agreement. This agreement shall inure to
the benefit of your successors and assigns and shall be binding upon our heirs.
administrators, executors, legal representatives, successors and assigns.

         IN WITNESS WHEREOF, this agreement is executed this___ day of___, ___.

                                      CYTOKINETICS, INCORPORATED
                                      (Name of Proprietorship, Partnership or
                                          Corporation, as applicable)

                                      By: /s/ James Sabry
                                          --------------------------------------
                                          (Signature)

                                      Title:____________________________________
                                            (Owner, Partner or Officer, as
                                               applicable)

                                      Address: 280 East Grand Avenue Suite 2,
                                               South San Francisco, CA 94080<PAGE>

                                                                     Exhibit 4.8

         THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933,
AS AMENDED (THE "ACT") AND MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED,
PLEDGED OR HYPOTHECATED UNLESS AND UNTIL REGISTERED UNDER THE ACT OR AN
EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF THE ACT IS AVAILABLE FOR SUCH
OFFER, SALE. OR TRANSFER, PLEDGE OR HYPOTHECATION IN THE OPINION OF LEGAL
COUNSEL REASONABLY SATISFACTORY TO THE COMPANY.

                                     WARRANT

                      To Purchase Shares of Common Stock of
                               CYTOKINETICS, INC.

         THIS CERTIFIES that, for value received Bristow Investments, L.P., a
California limited partnership (the "Holder"), is entitled, upon the terms and
subject to the conditions hereinafter set forth, at any time after the date
hereof and prior to the Commencement Date (as defined below), to subscribe for
and purchase from Cytokinetics, Inc., a Delaware corporation (the "Company"),
16,000 shares of the Company's Common Stock at an exercise price ("Exercise
Price") of $0.29 per share, subject to adjustment as set forth below.

         1. Title of Warrant. Prior to the expiration hereof and subject to
compliance with applicable laws, this Warrant and all rights hereunder are
transferable, in whole or in part, at the office or agency of the Company,
referred to in Section 2 hereof, by the holder hereof in person or by duly
authorized attorney, upon surrender of this Warrant together with the Assignment
Form annexed hereto properly endorsed.

         2. Exercise of Warrant. The purchase rights represented by this Warrant
are exercisable by the registered holder hereof, in whole or in part, at any
time after the effective date of the assignment and assumption to and by the
Company of that certain Lease, dated April 13, 1998 (as amended) by and between
MetaXen, LLC and Britannia Pointe Grand Limited Partnership ("BPGLP") and prior
to the date that is five (5) years after the closing date of an underwritten
initial public offering ("IPO") of the Company's Common Stock pursuant to a
registration statement filed with the Securities and Exchange Commission (the
"SEC") under the Act, subject to adjustment as hereinafter provided, by the
surrender of this Warrant and the Notice of Exercise Form annexed hereto duly
executed at the office of the Company, in South San Francisco. California (or
such other office or agency of the Company as it may designate by notice in
writing to the registered holder hereof at the address of such holder appearing
on the books of the Company), and upon payment of the Exercise Price for the
shares thereby purchased (i) by cash or check or bank draft payable to the order
of the Company, (ii) by cancellation of indebtedness of the Company payable to
the holder hereof at the time of exercise, or (iii) by delivery of an election
in writing to receive a number of shares of Common Stock equal to the aggregate
number of shares of Common Stock subject to this Warrant (or the portion thereof
being cancelled upon such exercise), less that number of shares of Common Stock
having a fair market value as of such date equal to the aggregate Exercise Price
of the Warrant (or such

<PAGE>

portion thereof); whereupon the holder of this Warrant shall be entitled to
receive a certificate for the number of shares so purchased. The Company agrees
that if at the time of the surrender of this Warrant and purchase the holder
hereof shall be entitled to exercise this Warrant, the shares so purchased shall
be and be deemed to be issued to such holder as the record owner of such shares
as of the close of business on the date on which this Warrant shall have been
exercised as aforesaid. For purposes of clause (iii) of the preceding sentence,
the fair market value of one share of the Company's Common Stock shall be
determined as follows: (1) if the Company's Common Stock is listed on a national
stock exchange, on the NASDAQ National Market System or on any other
over-the-counter market, then such fair market value shall be the closing price
per share reported for such class on such national stock exchange or on the
NASDAQ National Market System, or the average of the final "bid" and "asked"
prices reported on such over-the-counter market, as applicable, at the close of
business on the date of calculation as reported in the Wall Street Journal; and
(2) if the Company's Common Stock is not listed on any national stock exchange,
on the NASDAQ National Market System or on any other over-the-counter market,
then the Board of Directors of the Company shall determine such fair market
value as of the date of calculation in its reasonable good faith judgment, and
shall (upon written request by the holder hereof) advise the holder hereof of
such determination prior to any decision by such holder to exercise its purchase
rights under this Warrant.

         Certificates for shares purchased hereunder shall be delivered to the
holder hereof within a reasonable time, but not later than ten (10) days, after
the date on which this Warrant shall have been exercised as aforesaid.

         If this Warrant is exercised with respect to less than all of the
shares covered hereby, the holder hereof shall be entitled to receive a new
Warrant, in this form, covering the number of shares with respect to which this
Warrant shall not have been exercised.

         The Company covenants that all shares of stock which may be issued upon
the exercise of rights represented by this Warrant will, upon exercise of the
rights represented by this Warrant, be duly authorized, validly issued, fully
paid and nonassessable and free from all taxes, liens and charges in respect of
the issue thereof (other than taxes in respect of any transfer occurring
contemporaneously with such issue).

         3. No Fractional Shares or Scrip. No fractional shares or scrip
representing fractional shares shall be issued upon the exercise of this
Warrant.

         4. Charges, Taxes and Expenses. Issuance of certificates for shares of
Common Stock upon the exercise of this Warrant shall be made without charge to
the holder hereof for any issue or transfer tax or other incidental expense in
respect of the issuance of such certificate, all of which taxes and expenses
shall be paid by the Company, and such certificates shall be issued in the name
of the holder of this Warrant or in such name or names as may be directed by the
holder of this Warrant; provided, however, that in the event certificates for
shares of Common Stock are to be issued in a name other than the name of the
holder of this Warrant, this Warrant when surrendered for exercise shall be
accompanied by the Assignment Form attached hereto duly executed by the holder
hereof; and provided further, that upon any transfer involved in the issuance or
delivery of any

                                      -2-
<PAGE>

certificates for shares of Common Stock, the Company may require, as a condition
thereto, the payment of a sum sufficient to reimburse it for any transfer tax
incidental thereto.

         5. No Rights as Shareholders. This Warrant does not entitle the holder
hereof to any voting rights or other rights as a shareholder of the Company
prior to the exercise hereof. Notwithstanding the foregoing, the Company shall,
upon written request by the holder hereof to the chief financial officer of the
Company from time to time (but not more often than twice in any 12-month period)
provide to such holder copies of the following documents within a reasonable
time after such request (but in all events only to the extent that, and no
sooner than the time that, such documents have been made available to the
Company's shareholders): (i) the Company's most recent audited annual financial
statements or, if audited statements are not available, then the Company's
unaudited annual financial statements as of the end of the Company's most
recently ended fiscal year and (ii) unaudited quarterly financial statements for
each quarter of the Company's fiscal year since the date of the annual financial
statements delivered pursuant to clause (i) above. Notwithstanding the preceding
sentence, during any period in which the Company has outstanding a class of
publicly-traded securities or is for any other reason reporting company under
the Securities Exchange Act of 1934, it shall be sufficient compliance with any
information request from the holder hereof pursuant to such sentence for the
Company to provide copies of its most recent Form 10-K and annual report, any
Form 10-Qs and/or Form 8-Ks filed by the Company with the SEC since the date of
such Form 10- K, and any proxy statements.

         6. Exchange and Registry of Warrant. This Warrant is exchangeable, upon
the surrender hereof by the registered holder at the above-mentioned office or
agency of the Company, for a new Warrant of like tenor and dated as of such
exchange.

         The Company shall maintain at the above-mentioned office or agency a
registry showing the name and address of the registered holder of this Warrant.
This Warrant may be surrendered for exchange, transfer or exercise, in
accordance with its terms, at such office or agency of the Company, and the
Company shall be entitled to rely in all respects, prior to written notice to
the contrary, upon such registry.

         7. Loss, Theft, Destruction or Mutilation of Warrant. Upon receipt by
the Company of evidence reasonably satisfactory to it (such as an affidavit of
the holder hereof) of the loss, theft, destruction or mutilation of this
Warrant, and in case of loss, theft or destruction, of indemnity or security
reasonably satisfactory to it, and upon reimbursement to the Company of all
reasonable expenses incidental thereto, and upon surrender and cancellation of
this Warrant, if mutilated, the Company will make and deliver a new Warrant of
like tenor and dated as of such cancellation, in lieu of this Warrant.

         8. Saturdays, Sundays, Holidays, etc. If the last or appointed day for
the taking of any action or the expiration of any right required or granted
herein shall be a Saturday or a Sunday or shall be a legal holiday, then such
action may be taken or such right may be exercised on the next succeeding day
not a legal holiday.

                                      -3-
<PAGE>

         9. Adjustment. The number of shares for which this Warrant is
exercisable and the time period for exercise are subject to adjustment from time
to time as follows:

                  (a) Reclassification, etc. If the Company at any time shall,
by subdivision, combination or reclassification of securities or otherwise,
change any of the securities to which purchase rights under this Warrant exist
into the same or a different number of securities of any class or classes, this
Warrant shall thereafter be to acquire such number and kind of securities as
would have been issuable as the result of such change with respect to the
securities which were subject to the purchase rights under this Warrant
immediately prior to such subdivision, combination, reclassification or other
change and the Exercise Price shall be proportionately adjusted.

                  (b) Cash Distributions. No adjustment on account of cash
dividends or interest on the Company's Common Stock or other securities
purchasable hereunder will be made to the Exercise Price.

                  (c) This warrant shall be deemed rescinded in the event that
the Company's assumption of that certain Lease, dated April 13, 1998 (as
amended) by and between BPGLP and MetaXen, LLC shall not have occurred by
September 30, 2000.

         10. Miscellaneous.

                  (a) Termination Upon Merger, Sale of Assets, etc. If at any
time after the date hereof the Company proposes to merge with or into any other
corporation, effect a consolidation or reorganization with or into any other
entity, or sell or convey all or substantially all of its assets to any other
entity (collectively, a "Merger"), the Company shall give the Holder written
notice ("Merger Notice") of such impending transaction not later than thirty
(30) days prior to the closing of such transaction. The Merger Notice shall
describe the material terms and conditions of the impending transaction,
including the aggregate value of consideration to be received by the Holder for
the shares underlying this Warrant on an as exercised basis, and the Company
shall thereafter give the Holder prompt notice of any material changes to such
terms and conditions.

                           (i)      If, pursuant to such Merger, the
shareholders of the Company receive solely cash and/or publicly traded
securities in exchange for their shares of stock in the Company, as stated in
the Merger Notice, and this Warrant has not been exercised prior to the closing
of such transaction, this Warrant shall terminate.

                           (ii)     Notwithstanding anything to the contrary,
if, pursuant to such Merger, the shareholders of the Company receive
non-publicly traded securities in exchange for their shares of stock in the
Company, or if the aggregate value of the consideration consisting of cash
and/or publicly traded securities to be received by the Holder for the
securities underlying this Warrant, as stated in the Merger Notice, does not
equal or exceed the aggregate Exercise Price of such underlying securities, then
this Warrant shall not terminate pursuant to the provisions of Section 10(a)(i)
above, and the Company shall, as a condition precedent to such transaction,
cause effective provisions to be made so that the holder hereof shall have the
right thereafter, by exercising this Warrant (in lieu of the shares of the
common stock of the Company immediately theretofore

                                      -4-
<PAGE>

purchasable and receivable upon exercise of this Warrant) to purchase the kind
and amount of shares of stock and other securities and property (including cash)
receivable upon such transaction. Any such provision shall include provisions
for adjustments in respect of such shares of stock and other securities and
property that shall be as nearly equivalent as may be practicable to the
adjustments provided for in this Warrant. The foregoing provisions of this
Section 10(a)(ii) shall similarly apply to successive transactions, unless this
Warrant is first terminated pusuant to the provisions of Section 10(a)(i) above.

                  (b) Issue Date. The provisions of this Warrant shall be
construed and shall be given effect in all respect as if it had been issued and
delivered by the Company on the date hereof. This Warrant shall be binding upon
any successors or assigns of the Company. This Warrant shall constitute a
contract under the laws of the State of California and for all purposes shall be
construed in accordance with and governed by the laws of said state.

                  (c) Restrictions. The holder hereof acknowledges that the
Common Stock acquired upon the exercise of this Warrant shall have restrictions
upon its resale imposed by state and federal securities laws.

                  (d) Authorized Shares. The Company covenants that during the
period the Warrant is exercisable, it will reserve from its authorized and
Unicode Common Stock a sufficient number of shares to provide for the issuance
of Common Stock upon the exercise of any purchase rights under this Warrant. The
Company further covenants that its issuance of this Warrant shall constitute
full authority to its officers who are charged with the duty of executing stock
certificates to execute and issue the necessary certificates for shares of the
Company's Common Stock upon the exercise of the purchase rights under this
Warrant.

                  (e) No Impairment. The Company will not, by amendment of its
Articles of Incorporation or any other voluntary action, avoid or seek to avoid
the observance or performance of any of the terms of this Warrant, but will at
all times in good faith assist in the carrying out of all such terms and in the
taking of all such action as may be necessary or appropriate in order to protect
the rights of the holder hereof against impairment.

                  (f) Notices of Record Date. In case:

                           (i)      the Company shall take a record of the
holders of its Common Stock for the purposes of entitling them to receive any
dividend (other than a cash dividend) or other distribution, or any right to
subscribe for, purchase or otherwise acquire any shares or stock of any class or
any other securities or property, or to receive any other right; or

                           (ii)     of any capital reorganization of the
Company, any reclassification of the capital stock of the Company, any
consolidation or merger of the Company with or into another corporation, or any
conveyance of all or substantially all of the assets of the Company to another
corporation; or

                                      -5-
<PAGE>

                           (iii)    of the voluntary or involuntary dissolution,
liquidation or winding-up of the Company;

         then, and in each such case, the Company will mail or cause to be
mailed to the holder of this Warrant a notice specifying, as the case may be,
(i) the date on which a record is to be taken for the purpose of such dividend,
distribution or right, and stating the amount and character of such dividend,
distribution or right, or (ii) the date on which such reorganization,
reclassification, consolidation, merger, conveyance, dissolution, liquidation or
winding-up is to take place, and the time, if any is to be fixed, as of which
the holders of record of Common Stock shall be entitled to exchange their shares
of Common Stock for securities or other property deliverable upon such
reorganization, reclassification, consolidation, merger, conveyance,
dissolution, liquidation or winding-up. Such notice shall be mailed at least
thirty (30) days prior to the date therein specified.

                  (g) Attorneys' Fees. In any litigation, arbitration or other
legal proceeding between the Company and the holder hereto relating to or
arising out of this Warrant, the prevailing party shall be entitled to recover
all its fees, costs and expenses incurred in connection with such proceeding,
including (but not limited to) reasonable fees and expenses of attorneys and
accountants and including (but not limited to) all such fees, costs and expenses
incurred in connection with any appeals and/or in connection with the
enforcement of any judgment or award rendered in such proceeding.

                                      -6-
<PAGE>

         IN WITNESS WHEREOF, Cytokinetics, Inc. has caused this Warrant to be
executed by its officers thereunto duly authorized.

         Dated: July 20, 1999

         CYTOKINETICS, INC.

         By: /s/ James Sabry
             -------------------------
         Title: CEO & President

                                      -7-
<PAGE>

                               NOTICE OF EXERCISE

         To: CYTOKINETICS, INC.

         (1)      __________________, the undersigned, hereby elects to purchase
____________________________shares of Common Stock (the "Shares") at an exercise
price of $0.29 per share of Cytokinetics, Inc. pursuant to the terms of the
attached Warrant, and tenders herewith payment of the aggregate purchase price
of $____________in full (if exercising pursuant to net exercise provisions,
enter $-0-), together with all applicable transfer taxes, if any:

                  (choose one)

                  [ ]      By cash, check or sale draft payable to Cytokinetics,
                           Inc.; or

                  [ ]      By cancellation of indebtedness of Cytokinetics,
                           Inc., payable to the undersigned as of the date
                           hereof; or

                  [ ]      By net exercise pursuant to the provisions of Section
                           2(iii) of the attached warrant (no tender of payment
                           for the Shares needed).

         (2)      Please issue a certificate or certificates representing the
Shares (or the number of shares of Common Stock remaining after application of
the net exercise provisions of Section 2 (iii) of the attached warrant) in the
name of the undersigned or in such other name as is specified below:

         _______________________________
         (Name)

         _______________________________

         _______________________________
         (Address)

         (3)      The undersigned represents that the aforesaid shares of Common
Stock are being acquired for the account of the undersigned for investment and
not with a view to, or for resale in connection with, the distribution thereof
and that the undersigned has no present intention of distributing or reselling
such shares.

         ____________________________________________________________
         (Date) (Signature)

                                      -8-
<PAGE>

                                 ASSIGNMENT FORM

(To assign the foregoing warrant, execute this form and supply required
information. Do not use this form to purchase shares.)

         FOR VALUE RECEIVED, the foregoing Warrant and all rights evidenced
thereby are hereby assigned to

         ________________________________________
         (Please Print)

         whose address is _______________________

                          _______________________
                          (Please Print)

         Dated: _____________________,___________.

         Holder's Signature: ____________________

         Holder's Address: ______________________

                           ______________________

         NOTE: The signature to this Assignment Form must correspond with the
name as it appears on the face of the Warrant, without alteration or enlargement
or any change whatever, and must be guaranteed by a bank or trust company.
Officers of corporations and those acting in a fiduciary or other representative
capacity should file proper evidence of authority to assign the foregoing
Warrant.

                                      -9-

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