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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 N4cQ3nFb4bu9PQyeNG2hLm1gQ9uOBcFI9yYcYfeDW2IdP0K4pcvXSqQKK6iZ+Vab
 R3A8msChZr0q7rC77ZT1NQ==

<SEC-DOCUMENT>0001181431-07-059114.txt : 20070927
<SEC-HEADER>0001181431-07-059114.hdr.sgml : 20070927
<ACCEPTANCE-DATETIME>20070927171740
ACCESSION NUMBER:		0001181431-07-059114
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20070926
FILED AS OF DATE:		20070927
DATE AS OF CHANGE:		20070927

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			KOSAN BIOSCIENCES INC
		CENTRAL INDEX KEY:			0001110206
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-COMMERCIAL PHYSICAL & BIOLOGICAL RESEARCH [8731]
		IRS NUMBER:				943217016
		STATE OF INCORPORATION:			CA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		3832 BAY CENTER PLACE
		CITY:			HAYWARD
		STATE:			CA
		ZIP:			94545
		BUSINESS PHONE:		5107328400

	MAIL ADDRESS:	
		STREET 1:		3832 BAY CENTER PLACE
		CITY:			HAYWARD
		STATE:			CA
		ZIP:			94545

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			JOHNSON ROBERT G JR MD PHD
		CENTRAL INDEX KEY:			0001226065

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-31633
		FILM NUMBER:		071140030

	BUSINESS ADDRESS:	
		STREET 1:		C/O KOSAN BIOSCIENCES
		STREET 2:		3832 BAY CENTER PALCE
		CITY:			HAYWARD
		STATE:			CA
		ZIP:			94545
		BUSINESS PHONE:		5107328400
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>rrd173540.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2007-09-26</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001110206</issuerCik>
        <issuerName>KOSAN BIOSCIENCES INC</issuerName>
        <issuerTradingSymbol>KOSN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001226065</rptOwnerCik>
            <rptOwnerName>JOHNSON ROBERT G JR MD PHD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>3832 BAY CENTER PLACE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>HAYWARD</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94545</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President and CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.87</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2007-09-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2017-09-26</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The option vests in 48 equal monthly installments</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Gary S. Titus  Attorney-in-Fact</signatureName>
        <signatureDate>2007-09-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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