<SEC-DOCUMENT>0000899243-22-019926.txt : 20220527
<SEC-HEADER>0000899243-22-019926.hdr.sgml : 20220527
<ACCEPTANCE-DATETIME>20220527161528
ACCESSION NUMBER:		0000899243-22-019926
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20220525
FILED AS OF DATE:		20220527
DATE AS OF CHANGE:		20220527

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Atkinson Edward Morrow III
		CENTRAL INDEX KEY:			0001914164

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-39122
		FILM NUMBER:		22977647

	MAIL ADDRESS:	
		STREET 1:		C/O 89BIO, INC.
		STREET 2:		142 SANSOME STREET, SECOND FLOOR
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94104

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:		142 SANSOME STREET
		STREET 2:		SECOND FLOOR
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94104
		BUSINESS PHONE:		(415) 432-9270

	MAIL ADDRESS:	
		STREET 1:		142 SANSOME STREET
		STREET 2:		SECOND FLOOR
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94104
</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>2022-05-25</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001914164</rptOwnerCik>
            <rptOwnerName>Atkinson Edward Morrow III</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>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>2.61</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2022-05-25</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>6250</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2032-05-25</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>6250</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6250</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 6,250 shares of the Issuer's Common Stock, which will vest in full on May 16, 2023, subject to the Reporting Person's continued service to the Issuer through such date.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Ryan A. Murr, as attorney-in-fact for Edward Morrow Atkinson III</signatureName>
        <signatureDate>2022-05-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
