<SEC-DOCUMENT>0001628280-21-011544.txt : 20210602
<SEC-HEADER>0001628280-21-011544.hdr.sgml : 20210602
<ACCEPTANCE-DATETIME>20210602170322
ACCESSION NUMBER:		0001628280-21-011544
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20210602
FILED AS OF DATE:		20210602
DATE AS OF CHANGE:		20210602

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Stewart Murray
		CENTRAL INDEX KEY:			0001723450

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-38295
		FILM NUMBER:		21990036

	MAIL ADDRESS:	
		STREET 1:		C/O NOVELION THERAPEUTICS INC.
		STREET 2:		1800-510 WEST GEORGIA STREET
		CITY:			VANCOUVER
		STATE:			A1
		ZIP:			V6B OM3

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:		61 NORTH BEACON STREET
		STREET 2:		4TH FLOOR
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02134
		BUSINESS PHONE:		857-529-8300

	MAIL ADDRESS:	
		STREET 1:		61 NORTH BEACON STREET
		STREET 2:		4TH FLOOR
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02134

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	Arsanis, Inc.
		DATE OF NAME CHANGE:	20100920
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_162266776504487.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-06-02</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001723450</rptOwnerCik>
            <rptOwnerName>Stewart Murray</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O X4 PHARMACEUTICALS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>61 NORTH BEACON STREET, 4TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02134</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>9.5</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2021-06-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>6000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>9.50</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2031-06-02</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>6000.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">8.3333% of the shares subject to the option shall vest on July 2, 2021, with the remainder vesting in equal monthly installments of 8.333% of the shares subject to the option until the 12-month anniversary of the date of the grant (or, if earlier, the date of the Issuer's next annual meeting of stockholders following the date of the grant) subject to the Reporting Person continuing to provide services through each such date.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Derek M. Meisner, attorney-in-fact</signatureName>
        <signatureDate>2021-06-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
