<SEC-DOCUMENT>0000899243-20-010402.txt : 20200407
<SEC-HEADER>0000899243-20-010402.hdr.sgml : 20200407
<ACCEPTANCE-DATETIME>20200407161529
ACCESSION NUMBER:		0000899243-20-010402
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20200405
FILED AS OF DATE:		20200407
DATE AS OF CHANGE:		20200407

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Grunberg Gregory
		CENTRAL INDEX KEY:			0001711080

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-39122
		FILM NUMBER:		20779884

	MAIL ADDRESS:	
		STREET 1:		100 BEAVER STREET
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02453

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			89bio, Inc.
		CENTRAL INDEX KEY:			0001785173
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				831114349
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		535 MISSION STREET
		STREET 2:		14TH FLOOR
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94105
		BUSINESS PHONE:		4155004614

	MAIL ADDRESS:	
		STREET 1:		535 MISSION STREET
		STREET 2:		14TH FLOOR
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94105
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc4.xml
<DESCRIPTION>FORM 4 SUBMISSION
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2020-04-05</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001785173</issuerCik>
        <issuerName>89bio, Inc.</issuerName>
        <issuerTradingSymbol>ETNB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001711080</rptOwnerCik>
            <rptOwnerName>Grunberg Gregory</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O 89BIO, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>142 SANSOME STREET, 2ND FLOOR</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94104</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>21.40</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2020-04-05</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>7000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2030-04-05</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>7000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">This option represents a right to purchase a total of 7,000 shares of the Issuer's Common Stock, one third of which will vest on April 5, 2021, with the remaining two thirds vesting in equal monthly installments over the following two years, subject to the Reporting Person's continued service to the Issuer through each vesting date.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Ryan A. Murr, as attorney-in-fact for Gregory Grunberg</signatureName>
        <signatureDate>2020-04-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
