<SEC-DOCUMENT>0001104659-18-059933.txt : 20181002
<SEC-HEADER>0001104659-18-059933.hdr.sgml : 20181002
<ACCEPTANCE-DATETIME>20181002143154
ACCESSION NUMBER:		0001104659-18-059933
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20181001
FILED AS OF DATE:		20181002
DATE AS OF CHANGE:		20181002

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Merck & Co., Inc.
		CENTRAL INDEX KEY:			0000310158
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		STATE OF INCORPORATION:			NJ
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-38662
		FILM NUMBER:		181100785

	BUSINESS ADDRESS:	
		STREET 1:		2000 GALLOPING HILL ROAD
		CITY:			KENILWORTH
		STATE:			NJ
		ZIP:			07033
		BUSINESS PHONE:		908-740-4000

	MAIL ADDRESS:	
		STREET 1:		2000 GALLOPING HILL ROAD
		CITY:			KENILWORTH
		STATE:			NJ
		ZIP:			07033

	FORMER NAME:	
		FORMER CONFORMED NAME:	Merck & Co. Inc.
		DATE OF NAME CHANGE:	20091103

	FORMER NAME:	
		FORMER CONFORMED NAME:	SCHERING PLOUGH CORP
		DATE OF NAME CHANGE:	19920703

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Merck Sharp & Dohme Corp.
		CENTRAL INDEX KEY:			0000942443
		STATE OF INCORPORATION:			NJ
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-38662
		FILM NUMBER:		181100786

	BUSINESS ADDRESS:	
		STREET 1:		ONE MERCK DRIVE
		CITY:			WHITEHOUSE STATION
		STATE:			NJ
		ZIP:			08889
		BUSINESS PHONE:		908-740-4000

	MAIL ADDRESS:	
		STREET 1:		ONE MERCK DRIVE
		CITY:			WHITEHOUSE STATION
		STATE:			NJ
		ZIP:			08889

	FORMER NAME:	
		FORMER CONFORMED NAME:	SCHERING CORP
		DATE OF NAME CHANGE:	19950321

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			SUTRO BIOPHARMA INC
		CENTRAL INDEX KEY:			0001382101
		STANDARD INDUSTRIAL CLASSIFICATION:	BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
		IRS NUMBER:				452441988
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		310 UTAH AVE., SUITE 150
		CITY:			SOUTH SAN FRANCISCO
		STATE:			CA
		ZIP:			94080
		BUSINESS PHONE:		650-392-8412

	MAIL ADDRESS:	
		STREET 1:		310 UTAH AVE., SUITE 150
		CITY:			SOUTH SAN FRANCISCO
		STATE:			CA
		ZIP:			94080
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>a4.xml
<DESCRIPTION>4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-10-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001382101</issuerCik>
        <issuerName>SUTRO BIOPHARMA INC</issuerName>
        <issuerTradingSymbol>STRO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000310158</rptOwnerCik>
            <rptOwnerName>Merck &amp; Co., Inc.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2000 GALLOPING HILL ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>KENILWORTH</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07033</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000942443</rptOwnerCik>
            <rptOwnerName>Merck Sharp &amp; Dohme Corp.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE MERCK DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>WHITEHOUSE STATION</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>08889</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2018-10-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>C</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2056843</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2056843</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2018-10-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>666666</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>15</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2723509</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Series E Redeemable Convertible Preferred Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2018-10-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>C</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>74794315</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2056843</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Each share of Series E redeemable convertible preferred stock (the &quot;Series E Preferred&quot;) automatically converted into 0.0275 shares of the Issuer's common stock upon the closing of the Issuer's sale of its common stock in its firm commitment underwritten initial public offering pursuant to a registration statement on Form S-1 (File No. 333-227103) under the Securities Act of 1933, as amended. The Series E Preferred had no expiration date.</footnote>
        <footnote id="F2">These securities are owned directly by Merck Sharp &amp; Dohme Corp., which is a direct, wholly owned subsidiary of Merck &amp; Co., Inc. (&quot;Merck&quot;). Merck is an indirect beneficial owner of the reported securities.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Merck &amp; Co., Inc. /s/ Faye C. Brown, Senior Assistant Secretary</signatureName>
        <signatureDate>2018-10-02</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Merck Sharp &amp; Dohme Corp. /s/ Faye C. Brown, Assistant Secretary</signatureName>
        <signatureDate>2018-10-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
