# EDGAR Filing Document

**Accession Number:** 0001501697
**File Stem:** 9999999995-26-001669
**Filing Date:** 2026-5
**Character Count:** 1437
**Document Hash:** 36c13c9967baf23b75bf1cccc08a5a10
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**9999999995-26-001669.hdr.sgml**: 20260518

**ACCESSION NUMBER**: 9999999995-26-001669

**CONFORMED SUBMISSION TYPE**: EFFECT

**PUBLIC DOCUMENT COUNT**: 1

**FILED AS OF DATE**: 20260514

**DATE AS OF CHANGE**: 20260518

**EFFECTIVENESS DATE**: 20260514

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** X4 Pharmaceuticals, Inc
- **CENTRAL INDEX KEY:** 0001501697
- **STANDARD INDUSTRIAL CLASSIFICATION:** BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 273181608
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** EFFECT
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 333-295597
- **FILM NUMBER:** 26990657

**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

### UNITED STATES
### SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## Notice of Effectiveness

**Date:** May 14, 2026

**Time:** 16:15:00

**Form Type:** S-3

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**CIK:** 0001501697

**Company Name:** X4 Pharmaceuticals, Inc

**File Number:** 333-295597