X4制药美股招股说明书(2025-09-18版)

aggregate of 59,893,548 shares (the “Shares”) of common stock, par value $0.001 per share (“Common Stock”), of X4Pharmaceuticals, Inc. (“X4,” “we,” “our” or the “Company”), a Delaware corporation, consisting of (i) 11,040,776 shares ofCommon Stock and (ii) 48,852,772 shares of Common Stock issuable upon the exercise of pre-funded warrants with a per shareexercise price equal to $0.001 (the “Pre-Funded Warrants”). The Shares and the Pre-Funded Warrants were acquired by the Selling Stockholders pursuant to securities purchase agreements by andamong the Company and the Selling Stockholders, dated August11, 2025 and August12, 2025 (the “Purchase Agreements”). We areregistering the resale of the Shares covered by this prospectus as required by registration rights agreements by and among theCompany and the Selling Stockholders, dated August11, 2025 and August12, 2025 (the “Registration Rights Agreements”). We will not receive any of the proceeds from sales by the Selling Stockholders of the Shares, except the exercise price of $0.001 pershare of any of the Pre-Funded Warrants exercised by payment of cash. The Selling Stockholders may sell or otherwise dispose of the Shares covered by this prospectus in a number of different ways and atvarying prices. However, our registration of the Shares does not mean that the Selling Stockholders will offer or sell any of the Shares.We provide more information about how the Selling Stockholders may sell or otherwise dispose of the Shares covered by thisprospectus in the section entitled “Plan of Distribution” on page 14. Discounts, concessions, commissions and similar selling expensesattributable to the sale of the Shares covered by this prospectus will be borne by the Selling Stockholders. We will pay all expenses(other than discounts, concessions, commissions and similar selling expenses) relating to the registration of the Shares with theSecurities and Exchange Commission (the “SEC”). Our common stock is listed on The Nasdaq Capital Market (“Nasdaq”) under the symbol “XFOR.” On September 8, 2025, the lastreported sale price of our common stock on Nasdaq was $3.39 per share. Investing in our securities involves a high degree of risk. Before making any investment in our securities,you should consider carefully the risks and uncertainties described in the section entitled “Risk Factors”beginning on page 6 of this prospectus. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of thesesecurities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense. The date of this prospectus is September 17, 2025. Table of Contents ABOUT THIS PROSPECTUS1CAUTIONARY NOTE REGARDING FORWARD LOOKING STATEMENTS2PROSPECTUS SUMMARY4THE OFFERING5DISCLOSURE OF CERTAIN FINANCIAL DATA REFLECTING REVERSE STOCK SPLIT6RISK FACTORS7USE OF PROCEEDS8SELLING STOCKHOLDERS9PLAN OF DISTRIBUTION14LEGAL MATTERS16EXPERTS16WHERE YOU CAN FIND ADDITIONAL INFORMATION17INCORPORATION OF CERTAIN INFORMATION BY REFERENCE18 ABOUT THIS PROSPECTUSThis prospectus is part of a registration statement that we filed with the SEC utilizing a shelf registration process. Under the shelf registration process, the Selling Stockholders may, from time to time, offer and sell the Shares described in this prospectus in one ormore offerings. Information about the Selling Stockholders may change over time. This prospectus provides you with a general description of the Shares the Selling Stockholders may offer. Each time the SellingStockholders sell our Shares using this prospectus, to the extent necessary and required by law, we will provide a prospectussupplement that will contain specific information about the terms of that offering, including the number of Shares being offered, themanner of distribution, the identity of any underwriters or other counterparties and other specific terms related to the offering. Theprospectus supplement may also add, update or change information contained in this prospectus. To the extent that any statement madein a prospectus supplement is inconsistent with statements made in this prospectus, the statements made in this prospectus will bedeemed modified or superseded by those made in the prospectus supplement. You should read this prospectus, any applicableprospectus supplement and the information incorporated by reference in this prospectus before making an investment in shares of ourcommon stock. See “Where You Can Find Additional Information” and “Incorporation of Certain Information by Reference” for moreinformation. Neither we nor the Selling Stockholders have authorized anyone to provide any information other than that contained in thisprospectus or in any free writing prospectus prepared by or on behalf of us or to which we may have referred you. Neither we nor theSelling Stockholders take any responsibility for or provide assurance as to the reliability of, any other inf