<SEC-DOCUMENT>0001127602-25-014364.txt : 20250514
<SEC-HEADER>0001127602-25-014364.hdr.sgml : 20250514
<ACCEPTANCE-DATETIME>20250514194018
ACCESSION NUMBER:		0001127602-25-014364
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20250514
FILED AS OF DATE:		20250514
DATE AS OF CHANGE:		20250514

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			HENDERSON JOHN T
		CENTRAL INDEX KEY:			0001226488
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-50633
		FILM NUMBER:		25947863

	MAIL ADDRESS:	
		STREET 1:		320 WAKARA WAY
		CITY:			SALT LAKE CITY
		STATE:			UT
		ZIP:			84108

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CYTOKINETICS INC
		CENTRAL INDEX KEY:			0001061983
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		ORGANIZATION NAME:           	03 Life Sciences
		EIN:				943291317
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		350 OYSTER POINT BOULEVARD
		STREET 2:		.
		CITY:			SOUTH SAN FRANCISCO
		STATE:			CA
		ZIP:			94080
		BUSINESS PHONE:		(650) 624-3000

	MAIL ADDRESS:	
		STREET 1:		350 OYSTER POINT BOULEVARD
		CITY:			SOUTH SAN FRANCISCO
		STATE:			CA
		ZIP:			94080
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>form4.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-05-14</periodOfReport>

    <issuer>
        <issuerCik>0001061983</issuerCik>
        <issuerName>CYTOKINETICS INC</issuerName>
        <issuerTradingSymbol>CYTK</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001226488</rptOwnerCik>
            <rptOwnerName>HENDERSON JOHN T</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>350 OYSTER POINT BLVD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SOUTH SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94080</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-05-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>7333</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>73681</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>83</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>by Spouse</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Non-Qualified Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>30.00</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2025-05-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10880</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2025-06-16</value>
            </exerciseDate>
            <expirationDate>
                <value>2035-05-13</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10880</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>10880</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Comprised of restricted stock units (&quot;RSUs&quot;) that will vest in one installment on the earlier to occur of (x) the one-year anniversary of the grant date and (y) the date of the issuer's annual meeting of stockholders for the calendar year immediately subsequent to the grant date, subject to the director's continuous service as a member of the issuer's Board of Directors. RSUs convert to shares of common stock on a 1:1 basis upon vesting.</footnote>
        <footnote id="F2">Comprised of stock options that will vest monthly in equal installments over a period commencing on the grant date and ending on the earlier to occur of (x) the one-year anniversary of the date of the grant and (y) the date of the issuer's annual meeting of stockholders for the calendar year immediately subsequent to the grant date, subject to the director's continuous service as a member of the issuer's Board of Directors.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ John O. Faurescu, attorney-in-fact for Dr. Henderson</signatureName>
        <signatureDate>2025-05-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
