-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 SvR5mYRcUmMEZ7hMAu+WhyawJ05r5i77f7+JIbIP2yWHiZjUdTRpiXEfWhGLrB9d
 30kl0pA958t2uk2XIh6n1Q==

<SEC-DOCUMENT>0001140361-08-014461.txt : 20080605
<SEC-HEADER>0001140361-08-014461.hdr.sgml : 20080605
<ACCEPTANCE-DATETIME>20080605171939
ACCESSION NUMBER:		0001140361-08-014461
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20080605
FILED AS OF DATE:		20080605
DATE AS OF CHANGE:		20080605

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			SUNESIS PHARMACEUTICALS INC
		CENTRAL INDEX KEY:			0001061027
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				943295878
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		341 OYSTER POINT BOULEVARD
		CITY:			SOUTH SAN FRANCISCO
		STATE:			CA
		ZIP:			94080
		BUSINESS PHONE:		650-266-3500

	MAIL ADDRESS:	
		STREET 1:		341 OYSTER POINT BOULEVARD
		CITY:			SOUTH SAN FRANCISCO
		STATE:			CA
		ZIP:			94080

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	MOSAIC PHARMACEUTICALS INC
		DATE OF NAME CHANGE:	19980709

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Wells James A
		CENTRAL INDEX KEY:			0001321448

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-51531
		FILM NUMBER:		08883824

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		650-343-5656

	MAIL ADDRESS:	
		STREET 1:		1341 COLUMBUS AVENUE
		CITY:			BURLINGAME
		STATE:			CA
		ZIP:			94010
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-06-05</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001061027</issuerCik>
        <issuerName>SUNESIS PHARMACEUTICALS INC</issuerName>
        <issuerTradingSymbol>SNSS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001321448</rptOwnerCik>
            <rptOwnerName>Wells James A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O SUNESIS PHARMACEUTICALS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>341 OYSTER POINT BOULEVARD</rptOwnerStreet2>
            <rptOwnerCity>SOUTH SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94080</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Non-Qualified Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1.77</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2008-06-05</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2008-07-05</value>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2018-06-05</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>10000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">1/12 of the shares subject to the option will vest monthly commencing on June 5, 2008, such that 100% of the shares subject to the option will be fully vested and exercisable on June 5, 2009.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Camille L. Acayan, as attorney-in-fact for James A. Wells</signatureName>
        <signatureDate>2008-06-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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