-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 lNnCYC2Mnv3fC9oUjg2/lg==

<SEC-DOCUMENT>0001181431-07-059188.txt : 20070928
<SEC-HEADER>0001181431-07-059188.hdr.sgml : 20070928
<ACCEPTANCE-DATETIME>20070928062256
ACCESSION NUMBER:		0001181431-07-059188
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20070926
FILED AS OF DATE:		20070928
DATE AS OF CHANGE:		20070928

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/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-31633
		FILM NUMBER:		071140611

	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/A
<SEQUENCE>1
<FILENAME>rrd173571.xml
<DESCRIPTION>FORM 4/A
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4/A</documentType>

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

    <dateOfOriginalSubmission>2007-09-27</dateOfOriginalSubmission>

    <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>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2007-09-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>4.87</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>68360</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <remarks>1. We are filing this amendment to correctly reflect the open market purchase, not the grant of stock options, as reflected in the original filing.

2. We are filing this second amendment to reflect transactions incorrectly reported by service provider.</remarks>

    <ownerSignature>
        <signatureName>/s/ Gary S. Titus Attorney-in-Fact</signatureName>
        <signatureDate>2007-09-28</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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