X4 Pharmaceuticals Inc., together with its subsidiaries (the “Company”), is a biopharmaceutical company developing and commercializing novel therapeutics for the treatment of rare hematology diseases. The Company’s primary asset, mavorixafor, has received accelerated approval in the United States from the U.S. Food and Drug Administration (“FDA”) for use as an oral, once-daily therapy in patients 12 years of age and older with WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome, to increase the number of circulating mature neutrophils and lymphocytes. In addition, the European Commission has granted marketing authorization for mavorixafor capsules for the treatment of patients with WHIM syndrome in the European Union.

The Company continues to progress its global, pivotal, 52-week Phase 3 clinical trial, (the “4WARD” trial) to evaluate the efficacy, safety, and tolerability of oral, once-daily mavorixafor (with or without stable doses of granulocyte colony-stimulating factor (“G-CSF”)) in people with congenital, acquired primary autoimmune, or idiopathic chronic neutropenia (“CN”) who are experiencing recurrent and/or serious infections. CN is defined as periods lasting more than three months persistently or intermittently where there are abnormally low levels of neutrophils circulating in the blood, and may be idiopathic (of unknown origin), cyclic (episodes typically occurring every three weeks), or congenital (of genetic causation). CN disorders are rare blood conditions similarly characterized by increased risks of infections and cancer due to abnormally low levels of neutrophils in the body. In all cases, the CXCL12/CXCR4 pathway is the key regulator of neutrophil release from the bone marrow. Fast Track designation has been granted by the FDA to mavorixafor for the treatment of CN.

The accompanying unaudited interim condensed consolidated financial statements for the three and six months ended June 30, 2026 and 2025, respectively have been prepared in accordance with accounting principles generally accepted in the U.S. for interim financial information and with the instructions to the Quarterly Report on Form 10-Q and Article 10 of Regulation S-X. Accordingly, certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“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. 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 cash flows have been made. Operating results for the three and six months ended June 30, 2026 are not necessarily indicative of the results that may be expected for the entire year or for any other subsequent interim period.

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, 2025 included in its Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 17, 2026. The condensed consolidated balance sheet at December 31, 2025 that is presented in these interim condensed consolidated financial statements was derived from audited financial statements but does not include all disclosures required by GAAP.

The condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, including X4 Pharmaceuticals (Austria) GmbH, which is incorporated in Vienna, Austria, and X4 Therapeutics, Inc. All intercompany accounts and transactions have been eliminated.

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, 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.

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. For the six months ended June 30, 2026, the Company’s net loss was $36.4 million and net cash used in operating activities was $40.4 million. As of June 30, 2026, the Company had $208.0 million of cash, cash equivalents and short-term marketable securities, and an accumulated deficit of $631.0 million.

Based on its current operating plan, the Company believes (a) that its current cash, cash equivalents and short-term marketable securities will be sufficient to fund its operations and debt obligations for at least the next 12 months and (b) it will continue to comply with all covenants under the Hercules Loan Agreement, as defined and further described in Note 9, through at least the 12-month period from the issuance date of these condensed consolidated financial statements.

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 its 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.

The Company’s significant accounting policies are disclosed in the audited consolidated financial statements and the notes thereto in the Company’s Annual Report on Form 10-K for the year ended December 31, 2025 filed with the SEC on March 17, 2026. Since the date of those consolidated financial statements, there have been no material changes to the Company’s significant accounting policies.

Restricted Cash


(in thousands)	As of June 30, 2026		As of December 31, 2025
Letter of credit security: Vienna Austria lease	$	—	$	224
Letter of credit security: Boston lease	579		579
Letter of credit security: Watertown lease	95		—
Total restricted cash	$	674	$	803

In connection with the Company’s lease agreements for its facilities in Boston and Watertown, Massachusetts, the Company maintains letters of credit, which are secured by restricted cash, for the benefit of the respective landlords. As of December 31, 2025, restricted cash related to the Company’s former Vienna, Austria lease, which the Company terminated effective November 30, 2025, was included in other current assets and was subsequently converted to unrestricted cash during the six months ended June 30, 2026. Restricted cash related to the Boston and Watertown lease are included in other current assets and other assets, respectively.

The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the condensed consolidated balance sheets to the total of amounts shown in the Company’s condensed consolidated statements of cash flows as of June 30, 2026 and December 31, 2025:


(in thousands)	June 30, 2026		December 31, 2025
Cash and cash equivalents	$	195,095	$	217,049
Restricted cash, current (included within prepaid expenses and other current assets)	579		803
Restricted cash (included in other assets)	95		—
Total cash, cash equivalents and restricted cash	$	195,769	$	217,852

The Company’s cash equivalents consisted of money market funds invested in U.S. Treasury securities. The money market funds were valued based on quoted prices in active markets for identical assets, which represents a Level 1 measurement. All marketable securities are classified as short-term investments as all are due within one year and include investments in U.S. Treasury notes, U.S. Treasury bills and federal government agency notes. The amortized cost of each investment, individually and in aggregate, approximated fair value. The Company has evaluated each marketable security for impairment that is other-than-temporary and concluded that no marketable security was impaired as of June 30, 2026 and December 31, 2025.


	Fair Value Measurements as of June 30, 2026 Using:
(in thousands)	Level 1		Level 2		Level 3		Total

Cash equivalents—money market funds	$	191,613	$	—	$	—	$	191,613
Marketable securities—federal government agency notes	—		12,874		—		12,874
	$	191,613	$	12,874	$	—	$	204,487


	Fair Value Measurements as of December 31, 2025 Using:
(in thousands)	Level 1		Level 2		Level 3		Total

Cash equivalents—money market funds	$	123,838	$	—	$	—	$	123,838
Marketable securities—U.S. Treasury notes, U.S. Treasury bills, and federal government agency notes	—		35,949		—		35,949
	$	123,838	$	35,949	$	—	$	159,787


(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
U.S. Treasury securities	$	7,959	$	3	$	—	$	7,962
Federal Government Agency securities	27,980		11		4		27,987
Total available-for-sale debt securities	$	35,939	$	14	$	4	$	35,949

The following tables present information about the Company’s financial liabilities measured at fair value on a recurring basis and indicate the level of the fair value hierarchy used to determine such fair values:


	Fair Value Measurements as of June 30, 2026 Using:
(in thousands)	Level 1		Level 2		Level 3		Total




Liabilities:
Embedded derivative liability	$	—	$	—	$	10	$	10

Class C warrant liability	—		—		369		369
	$	—	$	—	$	379	$	379

Valuation of Embedded Derivative Liability— The fair value of the embedded derivative liability recognized in connection with the Company’s Hercules Loan Agreement, which is associated with additional fees due to Hercules upon non-credit related events of default, was determined based on significant inputs not observable in the market, which represents a Level 3 measurement within the fair value hierarchy. The fair value of this embedded derivative liability, which is reported within other non-current liabilities on the condensed consolidated balance sheets, is estimated by the Company at each reporting date based, in part, on the results of third-party valuations, which were prepared based on a discounted cash flow model that considered the timing and probability of occurrence of a redemption upon an event of default, the potential amount of prepayment fees or contingent interest upon an event of default and the Company’s risk-adjusted discount rate of 17%. As of June 30, 2026 and December 31, 2025, the fair value of this derivative liability was $10 thousand.

Class C Warrant Liability— In December 2022, the Company issued Class C warrants (“Class C Warrants”) for the purchase of shares of its common stock in a public offering. The Class C Warrants are accounted for as a liability on the condensed consolidated balance sheet and are adjusted to fair value at period end through “change in fair value of warrant liability” on the condensed consolidated statements of operations and comprehensive (loss) income.

Basic net loss per common share is calculated based on net loss divided by the weighted average number of shares outstanding for the period. The calculation of diluted loss per common share excludes the impact of potential common stock as their inclusion would be to reduce net loss per common share and are thus antidilutive.

Basic and diluted net loss per share was calculated as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
(in thousands, except share and per share data)	2026		2025		2026		2025
Numerator:
Net loss	$	(16,157)	$	(25,741)	$	(36,398)	$	(25,459)
Denominator:
Weighted average shares outstanding—basic and diluted	126,344,020		7,412,990		126,316,523		7,095,846
Net loss per share— basic and diluted	$	(0.13)	$	(3.47)	$	(0.29)	$	(3.59)

Basic and diluted weighted average shares of common stock outstanding for the three and six months ended June 30, 2026 and 2025 includes the weighted average effect of pre-funded warrants for the purchase of shares of common stock, for which the remaining unfunded exercise price is less than or equal to $0.03 per share.


	Three Months Ended June 30,		Six Months Ended June 30,
(in thousands)	2026	2025	2026	2025
Options to purchase shares of common stock	15,333	308	15,333	308
Unvested restricted stock units	714	333	714	333
Warrants to purchase shares of common stock (excluding prefunded warrants, which are included in basic shares outstanding)	2,546	2,546	2,546	2,546
	18,593	3,187	18,593	3,187

In November 2024, the FASB issued ASU 2024-03, Disaggregation of Income Statement Expenses (Topic 220) (“ASU 2024-03”, or “DISE”) requiring that public business entities disclose additional information about specific expense categories in the notes to financial statements at interim and annual reporting periods. The amendments in DISE are effective for annual reporting periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027. The