<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2014-11-25</periodOfReport>

    <dateOfOriginalSubmission>2014-11-25</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001618835</issuerCik>
        <issuerName>Neothetics, Inc.</issuerName>
        <issuerTradingSymbol>NEOT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001198325</rptOwnerCik>
            <rptOwnerName>JANNEY DANIEL</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE EMBARCADERO CENTER</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 3700</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94111</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001399763</rptOwnerCik>
            <rptOwnerName>Alta Partners VIII, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE EMBARCADERO CENTER</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 3700</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94111</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001399894</rptOwnerCik>
            <rptOwnerName>Alta Partners Management VIII, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE EMBARCADERO CENTER</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 3700</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94111</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001198321</rptOwnerCik>
            <rptOwnerName>CHAMPSI FARAH</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE EMBARCADERO CENTER</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 3700</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94111</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001198330</rptOwnerCik>
            <rptOwnerName>NOHRA GUY P</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE EMBARCADERO CENTER</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 3700</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94111</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>2014-11-25</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>X</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>93676</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>8.54</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2595257</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Alta Partners VIII, LP</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents shares as converted to Common Stock pursuant to the applicable conversion ratio, as listed in the Amended and Restated Certificate of Incorporation of the Issuer, and the 6.1-for-1 stock split of the Issuer's Common Stock which occurred on November 7, 2014.</footnote>
        <footnote id="F2">The original Form 4 Report filed on November 25, 2014 incorrectly stated the price as $11.29.</footnote>
        <footnote id="F3">The securities are held by Alta Partners VIII, L.P. (&quot;APVIII&quot;).  Alta Partners Management VIII, LLC (&quot;APMVIII&quot;) is the general partner of APVIII.  Guy Nohra, Daniel Janney and Farah Champsi are managing directors of APMVIII and exercise shared voting and investment power with respect to the shares owned by APVIII.  Each of the reporting persons disclaims beneficial ownership of such securities, except to the extent of his, her or its proportionate pecuniary interest therein.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ George Mahaffey, Attorney-in-fact</signatureName>
        <signatureDate>2014-12-01</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>George Mahaffey, Attorney-in-fact</signatureName>
        <signatureDate>2014-12-01</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>George Mahaffey, Attorney-in-fact</signatureName>
        <signatureDate>2014-12-01</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>George Mahaffey, Attorney-in-fact</signatureName>
        <signatureDate>2014-12-01</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>George Mahaffey, Attorney-in-fact</signatureName>
        <signatureDate>2014-12-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
