<SEC-DOCUMENT>0000899243-22-018588.txt : 20220518
<SEC-HEADER>0000899243-22-018588.hdr.sgml : 20220518
<ACCEPTANCE-DATETIME>20220518160941
ACCESSION NUMBER:		0000899243-22-018588
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20220516
FILED AS OF DATE:		20220518
DATE AS OF CHANGE:		20220518

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			DiRocco Derek
		CENTRAL INDEX KEY:			0001792061

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-39122
		FILM NUMBER:		22939189

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

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>2022-05-16</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001792061</rptOwnerCik>
            <rptOwnerName>DiRocco Derek</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>2.64</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2022-05-16</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>25000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2032-05-16</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>25000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25000</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 25,000 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 Derek DiRocco</signatureName>
        <signatureDate>2022-05-18</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
