X4 Pharmaceuticals, Inc

Our business is subject to various risks, including those described in Part I, Item 1A, “Risk Factors” of our Annual Report on Form 10-K for the year ended December 31, 2025. Except as set forth below, there have been no material changes from the risk factors disclosed in Item 1A of our Annual Report on Form 10-K for the year ended December 31, 2025. The risk factors set forth below should be read together with the risk factors described in our Annual Report on Form 10-K.

Risks Related to the Marketing and Commercialization of Our Product Candidates

The regulatory review and approval processes of the FDA and comparable foreign regulatory authorities are lengthy, time-consuming and inherently unpredictable, and if we are ultimately unable to obtain regulatory approval for our product candidates, including additional indications for mavorixafor, our business will be substantially harmed.

We are not permitted to market mavorixafor or any other product candidate in the United States until we receive approval of an NDA from the FDA, or in any foreign countries until we receive the requisite approval from such countries or jurisdictions, such as approval of the marketing authorization application in the European Union from the European Commission. Our future NDA submissions may receive a refusal to file response from the FDA, and even if filed by the FDA, we may receive a Complete Response Letter rather than approval for commercial marketing. In addition, we may be required by the FDA to conduct additional clinical trials and/or nonclinical studies to support potential approval. Successfully completing clinical trials and obtaining approval of an NDA is a complex, lengthy, expensive and uncertain process, and the FDA, or a comparable foreign regulatory authority, may delay, limit or deny approval of mavorixafor for the treatment of other indications for many reasons, including, among others:

•disagreement with the design or implementation and sufficiency of our clinical trials;

•failure to demonstrate the safety and efficacy of mavorixafor or any other product candidate for its proposed indications and that any clinical and other benefits of mavorixafor or any other product candidate outweigh its safety risks;

•deficiencies in the manufacturing or control processes or failure of third-party manufacturing facilities with which we contract for clinical and commercial supplies to comply with current cGMPs;

•insufficient data collected from clinical trials of mavorixafor or any other product candidate, or changes in the approval requirements that render its nonclinical and clinical data insufficient to support the filing of an NDA or to obtain regulatory approval; or

•changes in clinical practice in or approved products available for the treatment of the target patient population that could have an impact on the indications that we are pursuing for mavorixafor or our other product candidates.

For example, in August 2026, we received written responses from the FDA to our Type C meeting request regarding a reduction in the planned sample size of our Phase 3 4WARD trial of mavorixafor in chronic neutropenia from 176 to 126 participants. The FDA stated that, from a statistical perspective, the reduced sample size maintains adequate overall power for the trial’s co-primary endpoints. The FDA also requested that we provide detailed information, including our assumptions and supporting justification, to show that the reduced sample size maintains adequate power for all key secondary endpoints. In addition, the FDA stated that our proposed safety database appears acceptable to support an sNDA but that its adequacy remains a review issue. We intend to provide the requested information to the FDA. Even if the 4WARD trial meets its co-primary endpoints, it may not achieve statistical significance on one or more of its key secondary endpoints.

The FDA or a comparable foreign regulatory authority may also require more information, including additional nonclinical or clinical data to support approval, which may delay or prevent approval of our commercialization plans, or cause us to abandon the development program. If our current or future product candidates receive regulatory approval, these product candidates may be approved for fewer or more limited indications than we request, such approval may be contingent on the performance of costly post-marketing clinical trials, or we may not be allowed to include the labeling claims necessary or desirable for the successful commercialization of such product candidate.

Our term loan contains restrictions that limit our flexibility in operating our business.

Our K2 Loan Agreement is secured by a lien on substantially all of our assets, excluding intellectual property. This loan contains various covenants that limit our ability to engage in specified types of transactions. These covenants limit our ability to, among other things:

•dispose of assets;

•change our business, management, ownership or business locations;

•merge or consolidate;

•incur indebtedness;

•grant liens;

•pay dividends or make other distributions or repurchase equity;

•make investments and acquisitions;

•enter into exclusive licenses; or

•enter into transactions with affiliates

The K2 Loan Agreement also requires that (i) commencing October 1, 2027, at all times when our market capitalization is less than $800.0 million, we maintain unrestricted cash and cash equivalents of at least 75% of the total outstanding obligations under the K2 Loan Agreement, which threshold decreases to 40% following meeting certain conditions, and (ii) commencing April 1, 2029, we achieve trailing three-month net product revenue of at least 50% of the net product revenue set forth in our board-approved projections, and also subjects us to certain operational covenants.

None.