    <SEC-DOCUMENT>0001628280-23-012964-index.html : 20230425
    <SEC-HEADER>0001628280-23-012964.hdr.sgml : 20230425
    <ACCEPTANCE-DATETIME>20230425163555
    ACCESSION NUMBER:		0001628280-23-012964
    CONFORMED SUBMISSION TYPE:	ARS
    PUBLIC DOCUMENT COUNT:		1
    CONFORMED PERIOD OF REPORT:	20221231
    FILED AS OF DATE:		20230425
    DATE AS OF CHANGE:		20230425
    EFFECTIVENESS DATE:		20230425

    FILER:

    	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

    	FILING VALUES:
    		FORM TYPE:		ARS
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	001-38295
    		FILM NUMBER:		23845378

    	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>ARS
    <SEQUENCE>1
    <FILENAME>xfor-20221231x10k_ars.pdf
    <DESCRIPTION>ARS
    <TEXT>
    Document 1 - file: xfor-20221231x10k_ars.pdf

    </DOCUMENT>
    </SEC-DOCUMENT>