<SEC-DOCUMENT>0001562180-24-001219.txt : 20240209
<SEC-HEADER>0001562180-24-001219.hdr.sgml : 20240209
<ACCEPTANCE-DATETIME>20240209160449
ACCESSION NUMBER:		0001562180-24-001219
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		2
CONFORMED PERIOD OF REPORT:	20240207
FILED AS OF DATE:		20240209
DATE AS OF CHANGE:		20240209

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Jarrett Jennifer
		CENTRAL INDEX KEY:			0001671311
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-37708
		FILM NUMBER:		24614691

	MAIL ADDRESS:	
		STREET 1:		C/O MEDIVATION, INC.
		STREET 2:		525 MARKET ST., 36TH FLOOR
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94105

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Syndax Pharmaceuticals Inc
		CENTRAL INDEX KEY:			0001395937
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		ORGANIZATION NAME:           	03 Life Sciences
		IRS NUMBER:				320162505
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		35 GATEHOUSE DRIVE
		STREET 2:		BUILDING D, FLOOR 3
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02451
		BUSINESS PHONE:		781-419-1400

	MAIL ADDRESS:	
		STREET 1:		35 GATEHOUSE DRIVE
		STREET 2:		BUILDING D, FLOOR 3
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02451
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primarydocument.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-02-07</periodOfReport>

    <notSubjectToSection16>false</notSubjectToSection16>

    <issuer>
        <issuerCik>0001395937</issuerCik>
        <issuerName>Syndax Pharmaceuticals Inc</issuerName>
        <issuerTradingSymbol>SNDX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001671311</rptOwnerCik>
            <rptOwnerName>Jarrett Jennifer</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O SYNDAX PHARMACEUTICALS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>35 GATEHOUSE DRIVE, BUILDING D, FLOOR 3</rptOwnerStreet2>
            <rptOwnerCity>WALTHAM</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02451</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-02-07</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>17000.00</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>65000.00</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Award of Restricted Stock Units that vests one year from the date of grant. The shares underlying such Restricted Stock Units will not be delivered to the Reporting Person and may not be transferred or sold until the earlier of a separation from service, death, disability or change in control.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Michael A. Metzger, Attorney-in-Fact</signatureName>
        <signatureDate>2024-02-09</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-24
<SEQUENCE>2
<FILENAME>jarrettpoa.htm
<DESCRIPTION>JARRETTPOA.HTM
<TEXT>

<center><b>POWER OF ATTORNEY</b></center <br><br>

The undersigned, a member of the Board of Directors of Syndax
Pharmaceuticals, Inc., a Delaware corporation (the <u>"Company"</u>), hereby
constitutes and appoints Michael A. Metzger and Luke J. Albrecht, for so
long as each such person is an employee of the Company, and Laura Berezin,
for so long as she is a partner of a law firm representing the Company, the
undersigned's true and lawful attorney-in-fact, each with the power to act
alone for the undersigned and in the undersigned's name, place and stead, to:
<br><br>

1. Prepare, complete and execute Forms 3, 4 and 5 under the Securities
Exchange Act of 1934, as amended (the <u>"Exchange Act"</u>), and other forms
and all amendments thereto on the undersigned's behalf as such
attorney-in-fact shall in his or her discretion determine to be required or
advisable pursuant to Section 16 of the Exchange Act and the rules and
regulations promulgated thereunder, or any successor laws and regulations,
as a consequence of the undersigned's beneficial ownership of securities of
the Company or changes in such beneficial ownership; and <br><br>

2. Do all acts necessary in order to file such forms and amendments with the
 Securities and Exchange Commission, any securities exchange or national
association, the Company and such other persons or agencies as the
attorney-in-fact shall deem appropriate. <br><br>

The undersigned hereby ratifies and confirms all that said attorneys-in-fact
and agents shall do or cause to be done by virtue hereof. The undersigned
acknowledges that the foregoing attorneys-in-fact, in serving in such
capacity at the request of the undersigned, are not assuming, nor is the
Company assuming, any of the undersigned's responsibilities to comply with
or liability under Section 16 of the Exchange Act or any rules and
regulations promulgated thereunder or any successor laws and regulations.
<br><br>

This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4, or 5 with respect to
the undersigned's beneficial ownership of securities of the Company or
changes in such beneficial ownership, unless earlier revoked by the undersigned
in a signed writing delivered to the Company and the foregoing
attorneys-in-fact.<br><br>

The undersigned has executed this Power of Attorney as of September 27, 2018.
<br><br>


<u>/s/ Jennifer Jarrett</u><br>
Jennifer Jarrett
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
