<SEC-DOCUMENT>0001628280-20-013422.txt : 20200910
<SEC-HEADER>0001628280-20-013422.hdr.sgml : 20200910
<ACCEPTANCE-DATETIME>20200910083544
ACCESSION NUMBER:		0001628280-20-013422
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20200909
FILED AS OF DATE:		20200910
DATE AS OF CHANGE:		20200910

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Ragan Paula
		CENTRAL INDEX KEY:			0001769914

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-38295
		FILM NUMBER:		201167815

	MAIL ADDRESS:	
		STREET 1:		C/O X4 PHARMACEUTICALS, INC.
		STREET 2:		955 MASSACHUSETTS AVE., 4TH FLOOR
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02139

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			X4 Pharmaceuticals, Inc
		CENTRAL INDEX KEY:			0001501697
		STANDARD INDUSTRIAL CLASSIFICATION:	BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
		IRS NUMBER:				273181608
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		955 MASSACHUSETTS AVENUE
		STREET 2:		4TH FLOOR
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02139
		BUSINESS PHONE:		857-529-8300

	MAIL ADDRESS:	
		STREET 1:		955 MASSACHUSETTS AVENUE
		STREET 2:		4TH FLOOR
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02139

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	Arsanis, Inc.
		DATE OF NAME CHANGE:	20100920
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_159974132949074.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2020-09-09</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001501697</issuerCik>
        <issuerName>X4 Pharmaceuticals, Inc</issuerName>
        <issuerTradingSymbol>XFOR</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001769914</rptOwnerCik>
            <rptOwnerName>Ragan Paula</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O X4 PHARMACEUTICALS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>955 MASSACHUSETTS AVENUE, 4TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>CAMBRIGE</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02139</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President and CEO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2020-09-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>8840</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>8.04</value>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>287323</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The reported transaction was effected pursuant to a Rule 10b5-1 trading plan.</footnote>
        <footnote id="F2">Sale of shares to cover personal income tax obligation upon settlement of restricted stock unit award.</footnote>
        <footnote id="F3">The price reported is a weighted average price. These shares were sold in multiple transactions ranging from $7.56 to $8.96, inclusive. The Reporting Person undertakes to provide the Company, any security holder of the Company or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range.</footnote>
        <footnote id="F4">Of the shares of common stock reported, 101,714 shares represent unvested restricted stock units.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Derek M. Meisner, attorney-in-fact</signatureName>
        <signatureDate>2020-09-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
