<SEC-DOCUMENT>0000899243-19-011288.txt : 20190426
<SEC-HEADER>0000899243-19-011288.hdr.sgml : 20190426
<ACCEPTANCE-DATETIME>20190426195648
ACCESSION NUMBER:		0000899243-19-011288
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		2
CONFORMED PERIOD OF REPORT:	20190424
FILED AS OF DATE:		20190426
DATE AS OF CHANGE:		20190426

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Kelley Lynne E
		CENTRAL INDEX KEY:			0001667584

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-38295
		FILM NUMBER:		19773379

	MAIL ADDRESS:	
		STREET 1:		20451 SENECA MEADOWS PARKWAY
		CITY:			GERMANTOWN
		STATE:			MD
		ZIP:			20876

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>3
<SEQUENCE>1
<FILENAME>doc3.xml
<DESCRIPTION>FORM 3 SUBMISSION
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2019-04-24</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001667584</rptOwnerCik>
            <rptOwnerName>Kelley Lynne E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O X4 PHARMACEUTICALS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>955 MASSACHUSETTS AVENUE, 4TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>CAMBRIDGE</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02139</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>See Remarks</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <footnotes></footnotes>

    <remarks>Chief Medical Officer

Exhibit 24.1 - Power of Attorney</remarks>

    <ownerSignature>
        <signatureName>/s/ Adam S. Mostafa, attorney-in-fact</signatureName>
        <signatureDate>2019-04-26</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-24
<SEQUENCE>2
<FILENAME>attachment1.htm
<DESCRIPTION>EX-24 DOCUMENT
<TEXT>
<HTML>
<HEAD>
</HEAD>
<BODY>
<PRE>
                               POWER OF ATTORNEY

     Know all by these present, that the undersigned hereby constitutes and
appoints each of Paula Ragan, Ph.D., President and Chief Executive Officer of X4
Pharmaceuticals, Inc. (the "Company"), Adam S. Mostafa, Chief Financial Officer
of the Company, and Daniel T. Kajunski, John P. Condon, Christina S. Bailey,
Amanda Mei, Brenda L. Meyette and Anne T. Leland of Mintz, Levin, Cohn, Ferris,
Glovsky and Popeo, P.C., signing singly, with full power of substitution, the
undersigned's true and lawful attorney-in-fact to:

     (1)   execute for and on behalf of the undersigned, forms and
           authentication documents for EDGAR Filing Access;

     (2)   do and perform any and all acts for and on behalf of the undersigned
           which may be necessary or desirable to complete and execute any such
           forms and authentication documents;

     (3)   execute for and on behalf of the undersigned, in the undersigned's
           capacity as an officer, director and/or 10% shareholder of the
           Company, Forms 3, 4 and 5 in accordance with Section 16(a) of the
           Securities Exchange Act of 1934 and the rules thereunder;

     (4)   do and perform any and all acts for and on behalf of the undersigned
           which may be necessary or desirable to complete and execute any such
           Form 3, 4 or 5 and timely file such form with the United States
           Securities and Exchange Commission and any stock exchange or similar
           authority; and

     (5)   take any other action of any type whatsoever in connection with the
           foregoing which, in the opinion of such attorney-in-fact, may be of
           benefit to, in the best interests of, or legally required by the
           undersigned, it being understood that the documents executed by such
           attorney-in-fact on behalf of the undersigned pursuant to this Power
           of Attorney shall be in such form and shall contain such terms and
           conditions as such attorney-in-fact may approve in such attorney-in-
           fact's discretion.

     The undersigned hereby grants to each such attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary, or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all that such attorney-in-fact, or such
attorney-in-fact's substitute or substitutes, shall lawfully do or cause to be
done by virtue of this power of attorney and the rights and powers herein
granted. 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 Section 16 of the Securities Exchange Act of 1934, as amended.

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

     IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed this 22nd day of April, 2019.

                                        /s/ E. Lynne Kelley, M.D.
                                        ------------------------------
                                                 Signature

                                        E. Lynne Kelley, M.D.
                                        ------------------------------
                                                 Print Name


</PRE>
</BODY>
</HTML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
