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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-09-19</periodOfReport>

    <issuer>
        <issuerCik>0001069308</issuerCik>
        <issuerName>Acer Therapeutics Inc.</issuerName>
        <issuerTradingSymbol>ACER</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001599744</rptOwnerCik>
            <rptOwnerName>TVM Life Science Ventures VI GmbH &amp; Co KG</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O TVM CAPITAL GROUP</rptOwnerStreet1>
            <rptOwnerStreet2>OTTOSTRASSE 4</rptOwnerStreet2>
            <rptOwnerCity>MUNICH</rptOwnerCity>
            <rptOwnerState>2M</rptOwnerState>
            <rptOwnerZipCode>80333</rptOwnerZipCode>
            <rptOwnerStateDescription>GERMANY</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001318584</rptOwnerCik>
            <rptOwnerName>TVM Life Science Ventures VI LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O TVM CAPITAL GROUP</rptOwnerStreet1>
            <rptOwnerStreet2>OTTOSTRASSE 4</rptOwnerStreet2>
            <rptOwnerCity>MUNICH</rptOwnerCity>
            <rptOwnerState>2M</rptOwnerState>
            <rptOwnerZipCode>80333</rptOwnerZipCode>
            <rptOwnerStateDescription>GERMANY</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001640880</rptOwnerCik>
            <rptOwnerName>TVM Life Science Ventures VII L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O TVM CAPITAL GROUP</rptOwnerStreet1>
            <rptOwnerStreet2>204, RUE NOTRE-DAME OUEST, BUREAU 350</rptOwnerStreet2>
            <rptOwnerCity>MONTREAL</rptOwnerCity>
            <rptOwnerState>A8</rptOwnerState>
            <rptOwnerZipCode>H2Y 1T3</rptOwnerZipCode>
            <rptOwnerStateDescription>QUEBEC, CANADA</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001398598</rptOwnerCik>
            <rptOwnerName>Birner Hubert</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O TVM CAPITAL GROUP</rptOwnerStreet1>
            <rptOwnerStreet2>OTTOSTRASSE 4</rptOwnerStreet2>
            <rptOwnerCity>MUNICH</rptOwnerCity>
            <rptOwnerState>2M</rptOwnerState>
            <rptOwnerZipCode>80333</rptOwnerZipCode>
            <rptOwnerStateDescription>GERMANY</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001639971</rptOwnerCik>
            <rptOwnerName>Marengere Luc</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O TVM CAPITAL GROUP</rptOwnerStreet1>
            <rptOwnerStreet2>OTTOSTRASSE 4</rptOwnerStreet2>
            <rptOwnerCity>MUNICH</rptOwnerCity>
            <rptOwnerState>2M</rptOwnerState>
            <rptOwnerZipCode>80333</rptOwnerZipCode>
            <rptOwnerStateDescription>GERMANY</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001398596</rptOwnerCik>
            <rptOwnerName>Fischer Stefan</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O TVM CAPITAL GROUP</rptOwnerStreet1>
            <rptOwnerStreet2>OTTOSTRASSE 4</rptOwnerStreet2>
            <rptOwnerCity>MUNICH</rptOwnerCity>
            <rptOwnerState>2M</rptOwnerState>
            <rptOwnerZipCode>80333</rptOwnerZipCode>
            <rptOwnerStateDescription>GERMANY</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001133921</rptOwnerCik>
            <rptOwnerName>SCHUHSLER HELMUT</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O TVM CAPITAL GROUP</rptOwnerStreet1>
            <rptOwnerStreet2>OTTOSTRASSE 4</rptOwnerStreet2>
            <rptOwnerCity>MUNICH</rptOwnerCity>
            <rptOwnerState>2M</rptOwnerState>
            <rptOwnerZipCode>80333</rptOwnerZipCode>
            <rptOwnerStateDescription>GERMANY</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001718086</rptOwnerCik>
            <rptOwnerName>Wanless Mark</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O TVM CAPITAL GROUP</rptOwnerStreet1>
            <rptOwnerStreet2>OTTOSTRASSE 4</rptOwnerStreet2>
            <rptOwnerCity>MUNICH</rptOwnerCity>
            <rptOwnerState>2M</rptOwnerState>
            <rptOwnerZipCode>80333</rptOwnerZipCode>
            <rptOwnerStateDescription>GERMANY</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001718117</rptOwnerCik>
            <rptOwnerName>Leatt Gary</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O TVM CAPITAL GROUP</rptOwnerStreet1>
            <rptOwnerStreet2>OTTOSTRASSE 4</rptOwnerStreet2>
            <rptOwnerCity>MUNICH</rptOwnerCity>
            <rptOwnerState>2M</rptOwnerState>
            <rptOwnerZipCode>80333</rptOwnerZipCode>
            <rptOwnerStateDescription>GERMANY</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>2017-09-19</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>663782</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>663782</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>2017-09-19</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>227485</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>227485</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2017-09-19</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1172709</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1172709</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">These shares were acquired pursuant to an Agreement and Plan of Merger, dated as of June 30, 2017 (the &quot;Merger Agreement&quot;), pursuant to which a wholly-owned subsidiary of the Issuer merged with and into Acer Therapeutics Inc. (&quot;Acer&quot;). Pursuant to the Merger Agreement, at the Effective Time (as defined in the Merger Agreement) of the closing of the Mergers contemplated thereby, the then outstanding shares of Acer's common stock were cancelled and were automatically converted into the right to receive 1 share of the Issuer's common stock for each share of Acer common stock then held by the Reporting Persons. These shares were previously reported on a Form 3 filed by the Reporting Persons on the date of this filing.</footnote>
        <footnote id="F2">The shares are directly held by TVM Life Science Ventures VI GmbH &amp; Co. KG (&quot;TVM VI&quot;). Hubert Birner (&quot;Birner&quot;), Stefan Fischer (&quot;Fischer&quot;), and Helmut Schuhsler (&quot;Schuhsler&quot;) are members of the investment committee of TVM Life Science Ventures Management VI L.P. (&quot;TVM VI Management&quot;), a special limited partner of TVM VI, with voting and dispositive power over the shares held by TVM VI. TVM VI Management, Birner, Schuhsler and Fischer each disclaim beneficial ownership of the shares held by TVM VI, except to the extent of any pecuniary interest therein, if any. Birner is a director of the Issuer.</footnote>
        <footnote id="F3">The shares are directly held by TVM Life Science Ventures VI L.P. (&quot;TVM VI LP&quot;). Birner, Schuhsler and Fischer are members of the investment committee of TVM VI Management, a special limited partner of TVM VI LP, with voting and dispositive power over the shares held by TVM VI LP. TVM VI Management, Birner, Schuhsler and Fischer each disclaim beneficial ownership of the shares held by TVM VI LP, except to the extent of any pecuniary interest therein, if any.</footnote>
        <footnote id="F4">These shares are directly held by TVM Life Science Ventures VII L.P. (&quot;TVM VII LP&quot;). TVM Life Science Ventures VII (GP) Ltd. (&quot;TVM VII GP Ltd&quot;) is the general partner of TVM VII LP. Luc Marengere (&quot;Marengere&quot;), Mark Wanless (&quot;Wanless&quot;), Gary Leatt (&quot;Leatt&quot;), Birner, Fischer and Schuhsler are members of the investment committee of TVM VII GP Ltd, which has voting and investment power with respect to these shares. TVM VII GP Ltd, Birner, Fischer, Schuhsler, Marengere, Wanless and Leatt each disclaim any beneficial ownership of the reported securities, except to the extent of any pecuniary interest therein, if any. Marengere is a director of the Issuer.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Stefan Fischer, Director of TVM Life Science Ventures VI LLC, general partner of TVM Life Science Ventures Management VI L.P., managing limited partner of TVM Life Science Ventures VI GMBH &amp; Co. KG</signatureName>
        <signatureDate>2017-09-27</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Stefan Fischer, Director of TVM Life Science Ventures VI LLC, general partner of TVM Life Science Ventures Management VI L.P., managing limited partner of TVM Life Science Ventures VI L.P.</signatureName>
        <signatureDate>2017-09-27</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Stefan Fischer, Director of TVM Life Science Ventures VII (GP) Ltd., general partner of TVM Life Science Ventures VII L.P.</signatureName>
        <signatureDate>2017-09-27</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Stefan Fischer, Attorney in Fact for Hubert Birner</signatureName>
        <signatureDate>2017-09-27</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Luc Marengere</signatureName>
        <signatureDate>2017-09-27</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Stefan Fischer</signatureName>
        <signatureDate>2017-09-27</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Stefan Fischer, Attorney in Fact for Helmut Schuhsler</signatureName>
        <signatureDate>2017-09-27</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Mark Wanless</signatureName>
        <signatureDate>2017-09-27</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Gary Leatt</signatureName>
        <signatureDate>2017-09-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
