Nature of the Business and Basis of Presentation	6 Months Ended
Jun. 30, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of the Business and Basis of Presentation	NATURE OF THE BUSINESS AND BASIS OF PRESENTATION X4 Pharmaceuticals, Inc. (together with its subsidiaries, the “Company”) is a biopharmaceutical company developing and commercializing novel therapeutics for the treatment of rare diseases of the immune system. The Company has successfully developed its first product, mavorixafor, in its first indication. Mavorixafor is an orally available, small-molecule selective antagonist of chemokine receptor CXCR4. Due to its ability to increase the mobilization of mature, functional white blood cells from the bone marrow into the bloodstream, the Company believes that mavorixafor has the potential to benefit people with a range of immunodeficiencies - a therapeutic market that is principally served by injectable therapies frequently associated with treatment-limiting adverse events. On April 29, 2024, the Company announced that the U.S. Food and Drug Administration (“FDA”) approved the Company’s New Drug Application (“NDA”) for mavorixafor, which is being marketed in the U.S. under the trade name XOLREMDI®, for use as an oral, once-daily therapy in patients 12 years of age and older with WHIM syndrome (Warts, Hypogammaglobulinemia, Infections, and Myelokathexis), to increase the number of circulating mature neutrophils and lymphocytes. XOLREMDI is the first drug approved in the U.S. to treat patients with WHIM syndrome. The Company launched XOLREMDI in May 2024 and is currently marketing the drug in the U.S. through its X4 commercial team. WHIM syndrome is a rare combined primary immunodeficiency and chronic neutropenic disorder. The Company has filed for regulatory approvals to commercialize mavorixafor for the treatment of WHIM syndrome outside of the U.S. and is currently awaiting approval in the European union. The U.S. approval of mavorixafor in the WHIM syndrome indication is the first for mavorixafor. The Company has completed a Phase 2 study evaluating the safety and efficacy of mavorixafor as a monotherapy and in combination with granulocyte colony-stimulating factor (“G-CSF”) in people with certain other chronic neutropenic (“CN”) disorders beyond WHIM syndrome. Results from this six-month Phase 2 study showed mavorixafor was generally well tolerated and able to durably increase study participants’ mean absolute neutrophil count (“ANC”) both as a monotherapy and in combination with G-CSF. The Company is actively enrolling participants in a global, pivotal Phase 3 clinical trial of mavorixafor (the 4WARD study) that aims to evaluate the efficacy, safety, and tolerability of oral once-daily mavorixafor with or without G-CSF in people with congenital or acquired primary autoimmune and idiopathic chronic neutropenia who are experiencing recurrent and/or serious infections. The Company is headquartered in Boston, Massachusetts. Going Concern Assessment—The Company has evaluated whether there are certain conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the condensed consolidated financial statements are issued. Although the Company has an approved drug product, licensing and sales of the Company’s drug product over the next 12 months will not be sufficient to fund the Company’s operating expenses. Since inception, the Company has incurred significant operating losses and negative cash flows from operations, and the Company expects to continue to generate operating losses and negative cash flows from operations for the foreseeable future. As of June 30, 2025, the Company had $63.0 million of cash, cash equivalents and short-term marketable securities, and an accumulated deficit of $540.8 million. For the six months ended June 30, 2025, the Company’s net loss was $25.5 million and net cash used in operating activities was $42.3 million. The Company has a covenant (the “Minimum Cash Covenant”) under its Second Amended and Restated Loan and Security Agreement, as amended, (the “Hercules Loan Agreement”) with Hercules Capital Inc. (“Hercules”), that requires that the Company maintain a minimum level of cash of $15.0 million, which represents 20% of outstanding borrowings under the Hercules Loan Agreement. The Company must also continue to achieve a financial covenant (“Performance Covenant”), which includes maintaining a trailing six-month net product revenue of at least 55% of its forecast as approved by the Board of Directors. Such Performance Covenant is waived during any period in which: the Company maintains Qualified Cash, as defined in the Hercules Loan Agreement, in an aggregate amount equal to at least 75% of loans outstanding under the Hercules Loan Agreement or both (a) the Company maintains a Market Capitalization (as defined in the Hercules Loan Agreement) of at least $450.0 million and (b) the Company maintains Qualified Cash in an aggregate amount equal to at least 45% of loans outstanding. Based on its current operating plan, which includes estimates of anticipated cash inflows from product sales and cash outflows from operating expenses, the Company believes that it will not meet the conditions of the Performance Covenant and Minimum Cash Covenant within the 12-month period from the issuance date of these condensed consolidated financial statements. In such case, Hercules could accelerate the principal payments on the Company’s outstanding loans and the Company potentially would not have sufficient cash, cash equivalents and short-term marketable securities to settle such obligations. Accordingly, management has concluded that this condition meets the standard for raising substantial doubt about the Company’s ability to continue as a going concern. The Company does not have adequate financial resources to fund its forecasted operating costs for at least one year after the date that these condensed consolidated financial statements are issued. The accompanying condensed consolidated financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of this uncertainty. Accordingly, the condensed consolidated financial statements have been prepared on a basis that assumes the Company will continue as a going concern and that contemplates the realization of assets and satisfaction of liabilities and commitments in the ordinary course of business. To alleviate the risk that the Company violates the Performance Covenant or the Minimum Cash Covenant, the Company will need to raise additional capital, which cannot be assured, and/or modify the Performance Covenant and Minimum Cash Covenant. In addition, unless and until the Company reaches profitability in the future, it will require additional capital to fund its operations. Such additional capital could be raised through a combination of equity offerings, debt financings, other third-party funding, marketing and distribution arrangements, or other collaborations and strategic alliances. If the Company is unable to obtain funding, it could be forced to delay, reduce, or eliminate some or all of its research and development programs, product portfolio expansion or commercialization efforts, which would adversely affect its business prospects, or it may be unable to continue operations and may need to restructure its obligations in a court-supervised process or otherwise. The Company is subject to risks common to companies in the biopharmaceutical industry including, but not limited to, uncertainties relating to conducting preclinical and clinical research and development, the manufacture and supply of products and product candidates for clinical and commercial use, obtaining and maintaining regulatory approvals and pricing and reimbursement for the Company’s products and product candidates, market acceptance, managing global growth and operating expenses, availability of additional capital, competition, obtaining and enforcing patents, stock price volatility, dependence on collaborative relationships and third-party service providers, dependence on key personnel, and from time to time government investigations, litigation, and potential product liability claims. Principles of Consolidation— The condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, including X4 Pharmaceuticals (Austria) GmbH (“X4 Austria”), which is incorporated in Vienna, Austria, and X4 Therapeutics, Inc. All intercompany accounts and transactions have been eliminated. Reverse Stock Split— On April 28, 2025 the Company effected a 1-for-30 reverse stock split of its common stock (the “Reverse Stock Split”). Unless otherwise noted, all references to common stock share and per share amounts in this Quarterly Report on Form 10-Q have been retroactively adjusted to reflect the Reverse Stock Split. Unaudited Interim Condensed Consolidated Financial Statements— The condensed consolidated balance sheet at December 31, 2024 that is presented in these interim condensed consolidated financial statements was derived from audited financial statements but does not include all disclosures required by accounting principles generally accepted in the United States of America (“GAAP”). The accompanying condensed consolidated financial statements are unaudited. The accompanying unaudited interim condensed consolidated financial statements have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) for interim financial statements. Accordingly, certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. These unaudited interim condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements and the notes thereto for the year ended December 31, 2024 included in the 2024 Annual Report filed with the SEC on March 26, 2025. In the opinion of management, all adjustments, consisting only of normal recurring adjustments as necessary, for the fair statement of the Company’s condensed financial position, condensed results of its operations, and comprehensive (loss) income and cash flows have been made. The results of operations for the three and six months ended June 30, 2025 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2025. Use of Estimates— The preparation of the Company’s condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements, and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, the accrual of research and development expenses, the accrual of operational and financial license milestones (Note 3), the accrual of reserves for variable consideration related to product revenue, and the impairment or lack of impairment of long-lived assets including operating lease right-of-use assets and goodwill. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates when there are changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. As of the date of issuance of these condensed consolidated financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update its estimates, assumptions and judgments or revise the carrying value of its assets or liabilities. Actual results could differ from those estimates, and any such differences may be material to the Company’s condensed consolidated financial statements.

X4 Pharmaceuticals, Inc. (together with its subsidiaries, the “Company”) is a biopharmaceutical company developing and commercializing novel therapeutics for the treatment of rare diseases of the immune system. The Company has successfully developed its first product, mavorixafor, in its first indication. Mavorixafor is an orally available, small-molecule selective antagonist of chemokine receptor CXCR4. Due to its ability to increase the mobilization of mature, functional white blood cells from the bone marrow into the bloodstream, the Company believes that mavorixafor has the potential to benefit people with a range of immunodeficiencies - a therapeutic market that is principally served by injectable therapies frequently associated with treatment-limiting adverse events. On April 29, 2024, the Company announced that the U.S. Food and Drug Administration (“FDA”) approved the Company’s New Drug Application (“NDA”) for mavorixafor, which is being marketed in the U.S. under the trade name XOLREMDI®, for use as an oral, once-daily therapy in patients 12 years of age and older with WHIM syndrome (Warts, Hypogammaglobulinemia, Infections, and Myelokathexis), to increase the number of circulating mature neutrophils and lymphocytes. XOLREMDI is the first drug approved in the U.S. to treat patients with WHIM

syndrome. The Company launched XOLREMDI in May 2024 and is currently marketing the drug in the U.S. through its X4 commercial team. WHIM syndrome is a rare combined primary immunodeficiency and chronic neutropenic disorder. The Company has filed for regulatory approvals to commercialize mavorixafor for the treatment of WHIM syndrome outside of the U.S. and is currently awaiting approval in the European union. The U.S. approval of mavorixafor in the WHIM syndrome indication is the first for mavorixafor. The Company has completed a Phase 2 study evaluating the safety and efficacy of mavorixafor as a monotherapy and in combination with granulocyte colony-stimulating factor (“G-CSF”) in people with certain other chronic neutropenic (“CN”) disorders beyond WHIM syndrome. Results from this six-month Phase 2 study showed mavorixafor was generally well tolerated and able to durably increase study participants’ mean absolute neutrophil count (“ANC”) both as a monotherapy and in combination with G-CSF. The Company is actively enrolling participants in a global, pivotal Phase 3 clinical trial of mavorixafor (the 4WARD study) that aims to evaluate the efficacy, safety, and tolerability of oral once-daily mavorixafor with or without G-CSF in people with congenital or acquired primary autoimmune and idiopathic chronic neutropenia who are experiencing recurrent and/or serious infections. The Company is headquartered in Boston, Massachusetts.

Going Concern Assessment—The Company has evaluated whether there are certain conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the condensed consolidated financial statements are issued. Although the Company has an approved drug product, licensing and sales of the Company’s drug product over the next 12 months will not be sufficient to fund the Company’s operating expenses. Since inception, the Company has incurred significant operating losses and negative cash flows from operations, and the Company expects to continue to generate operating losses and negative cash flows from operations for the foreseeable future. As of June 30, 2025, the Company had $63.0 million of cash, cash equivalents and short-term marketable securities, and an accumulated deficit of $540.8 million. For the six months ended June 30, 2025, the Company’s net loss was $25.5 million and net cash used in operating activities was $42.3 million.

The Company has a covenant (the “Minimum Cash Covenant”) under its Second Amended and Restated Loan and Security Agreement, as amended, (the “Hercules Loan Agreement”) with Hercules Capital Inc. (“Hercules”), that requires that the Company maintain a minimum level of cash of $15.0 million, which represents 20% of outstanding borrowings under the Hercules Loan Agreement. The Company must also continue to achieve a financial covenant (“Performance Covenant”), which includes maintaining a trailing six-month net product revenue of at least 55% of its forecast as approved by the Board of Directors. Such Performance Covenant is waived during any period in which: the Company maintains Qualified Cash, as defined in the Hercules Loan Agreement, in an aggregate amount equal to at least 75% of loans outstanding under the Hercules Loan Agreement or both (a) the Company maintains a Market Capitalization (as defined in the Hercules Loan Agreement) of at least $450.0 million and (b) the Company maintains Qualified Cash in an aggregate amount equal to at least 45% of loans outstanding. Based on its current operating plan, which includes estimates of anticipated cash inflows from product sales and cash outflows from operating expenses, the Company believes that it will not meet the conditions of the Performance Covenant and Minimum Cash Covenant within the 12-month period from the issuance date of these condensed consolidated financial statements. In such case, Hercules could accelerate the principal payments on the Company’s outstanding loans and the Company potentially would not have sufficient cash, cash equivalents and short-term marketable securities to settle such obligations. Accordingly, management has concluded that this condition meets the standard for raising substantial doubt about the Company’s ability to continue as a going concern.

The Company does not have adequate financial resources to fund its forecasted operating costs for at least one year after the date that these condensed consolidated financial statements are issued. The accompanying condensed consolidated financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of this uncertainty. Accordingly, the condensed consolidated financial statements have been prepared on a basis that assumes the Company will continue as a going concern and that contemplates the realization of assets and satisfaction of liabilities and commitments in the ordinary course of business.

To alleviate the risk that the Company violates the Performance Covenant or the Minimum Cash Covenant, the Company will need to raise additional capital, which cannot be assured, and/or modify the Performance Covenant and Minimum Cash Covenant. In addition, unless and until the Company reaches profitability in the future, it will require additional capital to fund its operations. Such additional capital could be raised through a combination of equity offerings, debt financings, other third-party funding, marketing and distribution arrangements, or other collaborations and strategic alliances. If the Company is unable to obtain funding, it could be forced to delay, reduce, or eliminate some or all of its research and development programs, product portfolio expansion or commercialization efforts, which would adversely affect its business prospects, or it may be unable to continue operations and may need to restructure its obligations in a court-supervised process or otherwise.

The Company is subject to risks common to companies in the biopharmaceutical industry including, but not limited to, uncertainties relating to conducting preclinical and clinical research and development, the manufacture and supply of products and product candidates for clinical and commercial use, obtaining and maintaining regulatory approvals and pricing and reimbursement for the Company’s products and product candidates, market acceptance, managing global growth and operating expenses, availability of additional capital, competition, obtaining and enforcing patents, stock price volatility, dependence on collaborative relationships and third-party service providers, dependence on key personnel, and from time to time government investigations, litigation, and potential product liability claims.

Unaudited Interim Condensed Consolidated Financial Statements— The condensed consolidated balance sheet at December 31, 2024 that is presented in these interim condensed consolidated financial statements was derived from audited financial statements but does not include all disclosures required by accounting principles generally accepted in the United States of America (“GAAP”). The accompanying condensed consolidated financial statements are unaudited. The accompanying unaudited interim condensed consolidated financial statements have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) for interim financial statements. Accordingly, certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. These unaudited interim condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements and the notes thereto for the year ended December 31, 2024 included in the 2024 Annual Report filed with the SEC on March 26, 2025. In the opinion of management, all adjustments, consisting only of normal recurring adjustments as necessary, for the fair statement of the Company’s condensed financial position, condensed results of its operations, and comprehensive (loss) income and cash flows have been made. The results of operations for the three and six months ended June 30, 2025 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2025.

Use of Estimates— The preparation of the Company’s condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements, and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, the accrual of research and development expenses, the accrual of operational and financial license milestones (Note 3), the accrual of reserves for variable consideration related to product revenue, and the impairment or lack of impairment of long-lived assets including operating lease right-of-use assets and goodwill. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to

be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates when there are changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. As of the date of issuance of these condensed consolidated financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update its estimates, assumptions and judgments or revise the carrying value of its assets or liabilities. Actual results could differ from those estimates, and any such differences may be material to the Company’s condensed consolidated financial statements.