<SEC-DOCUMENT>0001588839-13-000001.txt : 20131009
<SEC-HEADER>0001588839-13-000001.hdr.sgml : 20131009
<ACCEPTANCE-DATETIME>20131009153353
ACCESSION NUMBER:		0001588839-13-000001
CONFORMED SUBMISSION TYPE:	D
PUBLIC DOCUMENT COUNT:		1
ITEM INFORMATION:		<ITEMS>06b
FILED AS OF DATE:		20131009
DATE AS OF CHANGE:		20131009
EFFECTIVENESS DATE:		20131009

FILER:

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MERSANA THERAPEUTICS INC
		CENTRAL INDEX KEY:			0001442836
		IRS NUMBER:				000000000
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		D
		SEC ACT:		1933 Act
		SEC FILE NUMBER:	021-204292
		FILM NUMBER:		131143363

	BUSINESS ADDRESS:	
		STREET 1:		840 MEMORIAL DRIVE
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02139
		BUSINESS PHONE:		617-498-0020

	MAIL ADDRESS:	
		STREET 1:		840 MEMORIAL DRIVE
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02139
</SEC-HEADER>
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<TYPE>D
<SEQUENCE>1
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        <entityName>MERSANA THERAPEUTICS INC</entityName>
        <issuerAddress>
            <street1>840 MEMORIAL DRIVE</street1>
            <city>CAMBRIDGE</city>
            <stateOrCountry>MA</stateOrCountry>
            <stateOrCountryDescription>MASSACHUSETTS</stateOrCountryDescription>
            <zipCode>02139</zipCode>
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        <jurisdictionOfInc>DELAWARE</jurisdictionOfInc>
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        <entityType>Corporation</entityType>
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            <relatedPersonName>
                <firstName>Nicholas</firstName>
                <middleName>G.</middleName>
                <lastName>Bacopoulos</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>840 Memorial Drive</street1>
                <city>Cambridge</city>
                <stateOrCountry>MA</stateOrCountry>
                <stateOrCountryDescription>MASSACHUSETTS</stateOrCountryDescription>
                <zipCode>02139</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Michael</firstName>
                <lastName>Metzger</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>840 Memorial Drive</street1>
                <city>Cambridge</city>
                <stateOrCountry>MA</stateOrCountry>
                <stateOrCountryDescription>MASSACHUSETTS</stateOrCountryDescription>
                <zipCode>02139</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Sara</firstName>
                <lastName>Nayeem</lastName>
            </relatedPersonName>
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                <city>Cambridge</city>
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            </relatedPersonName>
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                <zipCode>02139</zipCode>
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            <relatedPersonRelationshipList>
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                <firstName>Thomas</firstName>
                <lastName>Beck</lastName>
            </relatedPersonName>
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        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Timothy</firstName>
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            </relatedPersonName>
            <relatedPersonAddress>
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                <zipCode>02139</zipCode>
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        <relatedPersonInfo>
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                <firstName>Wayne</firstName>
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                <zipCode>02139</zipCode>
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            <relatedPersonRelationshipList>
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            </relatedPersonRelationshipList>
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    </relatedPersonsList>

    <offeringData>
        <industryGroup>
            <industryGroupType>Biotechnology</industryGroupType>
        </industryGroup>
        <issuerSize>
            <revenueRange>Decline to Disclose</revenueRange>
        </issuerSize>
        <federalExemptionsExclusions>
            <item>06b</item>
        </federalExemptionsExclusions>
        <typeOfFiling>
            <newOrAmendment>
                <isAmendment>false</isAmendment>
            </newOrAmendment>
            <dateOfFirstSale>
                <value>2013-09-27</value>
            </dateOfFirstSale>
        </typeOfFiling>
        <durationOfOffering>
            <moreThanOneYear>true</moreThanOneYear>
        </durationOfOffering>
        <typesOfSecuritiesOffered>
            <isEquityType>true</isEquityType>
            <isOptionToAcquireType>true</isOptionToAcquireType>
            <isSecurityToBeAcquiredType>true</isSecurityToBeAcquiredType>
        </typesOfSecuritiesOffered>
        <businessCombinationTransaction>
            <isBusinessCombinationTransaction>false</isBusinessCombinationTransaction>
            <clarificationOfResponse></clarificationOfResponse>
        </businessCombinationTransaction>
        <minimumInvestmentAccepted>0</minimumInvestmentAccepted>
        <salesCompensationList></salesCompensationList>
        <offeringSalesAmounts>
            <totalOfferingAmount>14499542</totalOfferingAmount>
            <totalAmountSold>4999994</totalAmountSold>
            <totalRemaining>9499548</totalRemaining>
            <clarificationOfResponse></clarificationOfResponse>
        </offeringSalesAmounts>
        <investors>
            <hasNonAccreditedInvestors>false</hasNonAccreditedInvestors>
            <totalNumberAlreadyInvested>7</totalNumberAlreadyInvested>
        </investors>
        <salesCommissionsFindersFees>
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                <dollarAmount>0</dollarAmount>
            </salesCommissions>
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            </findersFees>
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                <dollarAmount>0</dollarAmount>
            </grossProceedsUsed>
            <clarificationOfResponse></clarificationOfResponse>
        </useOfProceeds>
        <signatureBlock>
            <authorizedRepresentative>false</authorizedRepresentative>
            <signature>
                <issuerName>MERSANA THERAPEUTICS INC</issuerName>
                <signatureName>Wayne Foster</signatureName>
                <nameOfSigner>Wayne Foster</nameOfSigner>
                <signatureTitle>Vice President of Finance</signatureTitle>
                <signatureDate>2013-10-09</signatureDate>
            </signature>
        </signatureBlock>
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</SEC-DOCUMENT>
