License, Collaboration, and Funding Agreements	12 Months Ended
Dec. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
License, Collaboration, and Funding Agreements	LICENSE AND FUNDING ARRANGEMENTS Genzyme Agreement In July 2014, the Company entered into a license agreement with Genzyme (the “Genzyme Agreement”) pursuant to which the Company was granted an exclusive license to certain patents and intellectual property owned or controlled by Genzyme related to the CXCR4 receptor to develop and commercialize products containing licensed compounds (including but not limited to mavorixafor) for all therapeutic, prophylactic and diagnostic uses, with the exception of autologous and allogenic human stem cell therapy. Under the terms of the Genzyme Agreement, the Company is obligated to use commercially reasonable efforts to develop and commercialize licensed products for use in the field in the United States and at least one other major market country. The Company has the right to grant sublicenses of the licensed rights that cover mavorixafor to third parties. For the year ended December 31, 2024, a $7.0 million regulatory milestone payment was incurred and paid after receipt of FDA approval of the Company’s NDA on April 26, 2024. The payment was recorded as a definite-lived intangible asset as discussed in Note 8. For the year ended December 31, 2023, a $5.0 million milestone was incurred and paid upon the FDA’s acceptance of the Company’s NDA seeking approval of oral, once-daily mavorixafor in the treatment of people aged 12 years and older with WHIM syndrome. Such amount has been included within research and development expense. For the year ended December 31, 2022, the Company did not incur any payment obligations to Genzyme under the Genzyme Agreement. As of December 31, 2024, the Company is obligated to make future milestone payments in the aggregate amount of up to $13.0 million contingent upon the achievement by the Company of certain clinical-stage regulatory and sales milestones with respect to licensed products. The remaining regulatory milestones include (i) $3.0 million for the acceptance by the EMA of the Company’s first drug application and (ii) $5.0 million upon the notification by the EMA of regulatory approval of our first drug application. The Company must also make one-time sales milestone payments of $0.5 million, $1.5 million and $3.0 million on cumulative net sales of $50.0 million, $150.0 million and $300.0 million, respectively. As of December 31, 2024, the Company accrued $3.0 million of regulatory milestones, which were achieved and paid in the first quarter of 2025, and $0.5 million of sales-based milestones as a component of the definite-lived intangible asset, as management has concluded that the achievement of these milestones is probable. The Company is also obligated to pay Genzyme tiered royalties based on net sales of licensed products that the Company commercializes under the agreement. Upon the first sale of the Company’s drug candidate in the U.S., the Company incurred a royalty on annual net sales at a rate of 6%, and will incur royalties on annual net sales at a rate of 6% up to $150.0 million, 10% on the portion of annual net sales between $150.0 million and $300.0 million, and 12.00% thereafter on annual sale over $300.0 million. The Company also incurs a 15% royalty on certain sublicense payments received from sub-licensees. The obligation to pay royalties for each licensed product expires on a country-by-country basis on the latest of (i) the expiration of licensed patent rights that cover that licensed product in that country, (ii) the expiration of regulatory exclusivity in that country and (iii) ten years after the first commercial sale of such licensed product in that country. Royalty rates are subject to reduction under the agreement in specified circumstances, including in any country if the Company is required to obtain a license from any third party to the extent the Company’s patent rights might infringe the third party’s patent rights, if a licensed product is not covered by a valid claim in that country or if sales of generic products reach certain thresholds in that country. If the Company enters into a sublicense under the Genzyme Agreement, the Company will be obligated to pay Genzyme a percentage of certain upfront fees, maintenance fees, milestone payments and royalty payments paid to the Company by the sublicensee. Under the Genzyme Agreement, the Company will itself manufacture and supply, or enter into manufacturing or supply agreements with Genzyme or third parties to manufacture and supply, clinical and commercial supplies of licensed compounds and each licensed product. The Company is also responsible for all costs related to the filing, prosecution and maintenance of the licensed patent rights. The Genzyme Agreement will remain in effect until the expiration of the royalty term in all countries for all licensed products. The Genzyme Agreement may be terminated by either party with at least 90 days’ notice in the event of material breach by the other party that remains uncured for 90 days, by either party for insolvency or bankruptcy of the other party, immediately by Genzyme if the Company challenges the licensed patents, or immediately by the Company if a material safety issue arises. Georgetown Agreement In December 2016, the Company entered into a license agreement (the “Georgetown Agreement”) with Georgetown University (“Georgetown”) pursuant to which the Company obtained an exclusive, worldwide license to make, have made, use, sell, offer for sale and import of products covered by patent rights co-owned by Georgetown. The rights licensed to the Company are for all therapeutic, prophylactic and diagnostic uses in all disease indications in humans and animals. Under the terms of the Georgetown Agreement, the Company paid a one-time, upfront fee of $50 thousand, and the Company may be required to make milestone payments of up to an aggregate of $800 thousand related to commercial sales of its product. Under the Georgetown Agreement, the Company is solely responsible for all development and commercialization activities and costs in its respective territories. The Company is also responsible for all costs related to the filing, prosecution, and maintenance of the licensed patent rights. The term of the Georgetown Agreement will continue until the expiration of the last valid claim within the patent rights covering the product. Georgetown may terminate the agreement in the event (i) the Company fails to pay any amount and fails to cure such failure within 30 days after receipt of notice, (ii) the Company defaults in its obligation to obtain and maintain insurance and fails to remedy such breach within 45 days after receipt of notice, or (iii) the Company declares insolvency or bankruptcy. The Company may terminate the Georgetown Agreement at any time upon at least 60 days’ written notice. During the years ended December 31, 2024, 2023 and 2022, the Company did not incur any payment obligations to Georgetown under the Georgetown Agreement and no milestone payments were made or due under the Georgetown Agreement. Beth Israel Deaconess Medical Center Agreement In December 2016, the Company entered into a license agreement (the “BIDMC Agreement”) with Beth Israel Deaconess Medical Center (“BIDMC”), pursuant to which the Company obtained an exclusive, worldwide license to make, have made, use, sell, offer for sale and import products covered by patent rights co-owned by BIDMC. The rights licensed to the Company are for all fields of use. Under the terms of the BIDMC Agreement, the Company paid a one-time, upfront fee of $20 thousand, and the Company is responsible for all future patent prosecution costs. The Company recorded the upfront payment as research and development expense in the consolidated statements of operations and comprehensive loss because the acquired technology represented in-process research and development and had no alternative future use. The term of the BIDMC Agreement will continue until the expiration of the last valid claim within the patent rights covering the licensed products. BIDMC may terminate the agreement in the event (i) the Company fails to pay any amount and fails to cure such failure within 15 days after receipt of notice, (ii) the Company is in material breach of any material provision of the BIDMC Agreement and fails to remedy such breach within 60 days after receipt of notice, or (iii) the Company declares insolvency or bankruptcy. The Company may terminate the BIDMC Agreement at any time upon at least 90 days’ written notice. The Company did not incur any payment obligations under the BIDMC Agreement during the years ended December 31, 2024, 2023 and 2022. Dana Farber Cancer Institute Agreement In November 2020, the Company entered into a license agreement (the “DFCI Agreement”) with the Dana Farber Cancer Institute (“DFCI”) pursuant to which the Company obtained a non-exclusive, royalty-bearing license to use, make, have made, develop, market, import, distribute, sell and have sold products covered by patent rights owned by DFCI. Under the terms of the DFCI Agreement, the Company paid a one-time, upfront fee of $25 thousand and approximately $35 thousand for reimbursement of DFCI’s past patent expenses relating to the patent rights. The DFCI Agreement was terminated effective January 20, 2025 and the Company has no further rights or obligations under the DFCI Agreement. Research and Development Incentive Program The Company participates in a research and development incentive program provided by the Austrian government whereby the Company is entitled to reimbursement by the Austrian government for a percentage of qualifying research and development expenses incurred by the Company’s subsidiary in Austria. Under the program, the reimbursement rate for qualifying research and development expenses incurred by the Company through X4 Austria is 14% for the current year. The Company recognizes incentive income from Austrian research and development incentives when qualifying expenses have been incurred, there is reasonable assurance that the payment will be received, and the consideration can be reliably measured. Management has assessed the Company’s research and development activities and expenditures to determine which activities and expenditures are likely to be eligible under the research and development incentive program described above. At each reporting date, management estimates the reimbursable incentive income available to the Company based on available information at the time. As of the years ended December 31, 2024 and 2023, the amounts due under these programs were $0.7 million and $0.6 million, respectively, which is included in research and development incentive receivable on the consolidated balance sheets. During the years ended December 31, 2024, 2023 and 2022, the Company recorded $0.7 million, $0.6 million and $0.5 million, respectively, of income related to the program on the consolidated statements of operations and comprehensive loss within “other income”. Abbisko Agreement In July 2019, the Company entered into a license agreement with Abbisko (the “Abbisko Agreement”). Under the terms of the Abbisko Agreement, the Company granted Abbisko the exclusive right to develop, manufacture and commercialize mavorixafor in mainland China, Taiwan, Hong Kong and Macau, the (“Abbisko Territory”). The agreement provides Abbisko with the exclusive rights in the Abbisko Territory to develop and commercialize mavorixafor in combination with checkpoint inhibitors or other agents in multiple oncology indications. The Company retains the full rest-of-world rights to develop and commercialize mavorixafor outside of Greater China for all indications and the ability to utilize data generated pursuant to the Abbisko collaboration for rest-of-world development. Assuming mavorixafor is developed by Abbisko in six indications, the Company would be entitled to milestone payments of up to $214.0 million, which will vary based on the ultimate sales, if any, of the approved licensed products. In addition, upon commercialization of mavorixafor in the Abbisko Territory, the Company is eligible to receive a tiered royalty, with a percentage range in the low double-digits, on net sales of approved licensed products. Abbisko is obligated to use commercially reasonable efforts to develop and commercialize mavorixafor in the Abbisko Territory. Abbisko has responsibility for all activities and costs associated with the further development, manufacture and commercialization of mavorixafor in the Abbisko Territory. The Company determined that the future sale of clinical and commercial supply are optional goods that will be subject to the customer’s future purchasing decisions and do not represent performance obligations in the Abbisko Agreement. The Company concluded that the amount to be charged for the clinical supply will be reflective of market value and, therefore, the Abbisko Agreement does not provide a discount on such supply that would be accounted for as material right at the outset of the contract. In arriving at these conclusions, the Company considered the complexity of the manufacturing process for the licensed compound and the potential ability for Abbisko to obtain the compound directly from other manufactures in the future. The Company expects that it will recognize revenue at a point in time when such clinical supply (and commercial supply, if applicable) is delivered to Abbisko in the future. The Company re-evaluates the transaction price, including its estimated variable consideration for milestones included in the transaction price and all constrained amounts, in each reporting period and as uncertain events are resolved or other changes in circumstances occur. Norgine Agreement. See Note 20, Subsequent Events.

In July 2014, the Company entered into a license agreement with Genzyme (the “Genzyme Agreement”) pursuant to which the Company was granted an exclusive license to certain patents and intellectual property owned or controlled by Genzyme related to the CXCR4 receptor to develop and commercialize products containing licensed compounds (including but not limited to mavorixafor) for all therapeutic, prophylactic and diagnostic uses, with the exception of autologous and allogenic human stem cell therapy. Under the terms of the Genzyme Agreement, the Company is obligated to use commercially reasonable efforts to develop and commercialize licensed products for use in the field in the United States and at least one other major market country. The Company has the right to grant sublicenses of the licensed rights that cover mavorixafor to third parties.

For the year ended December 31, 2024, a $7.0 million regulatory milestone payment was incurred and paid after receipt of FDA approval of the Company’s NDA on April 26, 2024. The payment was recorded as a definite-lived intangible asset as discussed in Note 8. For the year ended December 31, 2023, a $5.0 million milestone was incurred and paid upon the FDA’s acceptance of the Company’s NDA seeking approval of oral, once-daily mavorixafor in the treatment of people aged 12 years and older with WHIM syndrome. Such amount has been included within research and development expense. For the year ended December 31, 2022, the Company did not incur any payment obligations to Genzyme under the Genzyme Agreement.

As of December 31, 2024, the Company is obligated to make future milestone payments in the aggregate amount of up to $13.0 million contingent upon the achievement by the Company of certain clinical-stage regulatory and sales milestones with respect to licensed products. The remaining regulatory milestones include (i) $3.0 million for the acceptance by the EMA of the Company’s first drug application and (ii) $5.0 million upon the notification by the EMA of regulatory approval of our first drug application. The Company must also make one-time sales milestone payments of $0.5 million, $1.5 million and $3.0 million on cumulative net

sales of $50.0 million, $150.0 million and $300.0 million, respectively. As of December 31, 2024, the Company accrued $3.0 million of regulatory milestones, which were achieved and paid in the first quarter of 2025, and $0.5 million of sales-based milestones as a component of the definite-lived intangible asset, as management has concluded that the achievement of these milestones is probable.

The Company is also obligated to pay Genzyme tiered royalties based on net sales of licensed products that the Company commercializes under the agreement. Upon the first sale of the Company’s drug candidate in the U.S., the Company incurred a royalty on annual net sales at a rate of 6%, and will incur royalties on annual net sales at a rate of 6% up to $150.0 million, 10% on the portion of annual net sales between $150.0 million and $300.0 million, and 12.00% thereafter on annual sale over $300.0 million. The Company also incurs a 15% royalty on certain sublicense payments received from sub-licensees.

The obligation to pay royalties for each licensed product expires on a country-by-country basis on the latest of (i) the expiration of licensed patent rights that cover that licensed product in that country, (ii) the expiration of regulatory exclusivity in that country and (iii) ten years after the first commercial sale of such licensed product in that country. Royalty rates are subject to reduction under the agreement in specified circumstances, including in any country if the Company is required to obtain a license from any third party to the extent the Company’s patent rights might infringe the third party’s patent rights, if a licensed product is not covered by a valid claim in that country or if sales of generic products reach certain thresholds in that country. If the Company enters into a sublicense under the Genzyme Agreement, the Company will be obligated to pay Genzyme a percentage of certain upfront fees, maintenance fees, milestone payments and royalty payments paid to the Company by the sublicensee. Under the Genzyme Agreement, the Company will itself manufacture and supply, or enter into manufacturing or supply agreements with Genzyme or third parties to manufacture and supply, clinical and commercial supplies of licensed compounds and each licensed product. The Company is also responsible for all costs related to the filing, prosecution and maintenance of the licensed patent rights.

The Genzyme Agreement will remain in effect until the expiration of the royalty term in all countries for all licensed products. The Genzyme Agreement may be terminated by either party with at least 90 days’ notice in the event of material breach by the other party that remains uncured for 90 days, by either party for insolvency or bankruptcy of the other party, immediately by Genzyme if the Company challenges the licensed patents, or immediately by the Company if a material safety issue arises.

In December 2016, the Company entered into a license agreement (the “Georgetown Agreement”) with Georgetown University (“Georgetown”) pursuant to which the Company obtained an exclusive, worldwide license to make, have made, use, sell, offer for sale and import of products covered by patent rights co-owned by Georgetown. The rights licensed to the Company are for all therapeutic, prophylactic and diagnostic uses in all disease indications in humans and animals.

Under the terms of the Georgetown Agreement, the Company paid a one-time, upfront fee of $50 thousand, and the Company may be required to make milestone payments of up to an aggregate of $800 thousand related to commercial sales of its product. Under the Georgetown Agreement, the Company is solely responsible for all development and commercialization activities and costs in its respective territories. The Company is also responsible for all costs related to the filing, prosecution, and maintenance of the licensed patent rights. The term of the Georgetown Agreement will continue until the expiration of the last valid claim within the patent rights covering the product. Georgetown may terminate the agreement in the event (i) the Company fails to pay any amount and fails to cure such failure within 30 days after receipt of notice, (ii) the Company defaults in its obligation to obtain and maintain insurance and fails to remedy such breach within 45 days after receipt of notice, or (iii) the Company declares insolvency or bankruptcy. The Company may terminate the Georgetown Agreement at any time upon at least 60 days’ written notice. During the years ended December 31, 2024, 2023 and 2022, the Company did not incur any payment obligations to Georgetown under the Georgetown Agreement and no milestone payments were made or due under the Georgetown Agreement.

In December 2016, the Company entered into a license agreement (the “BIDMC Agreement”) with Beth Israel Deaconess Medical Center (“BIDMC”), pursuant to which the Company obtained an exclusive, worldwide license to make, have made, use, sell, offer for sale and import products covered by patent rights co-owned by BIDMC. The rights licensed to the Company are for all fields of use. Under the terms of the BIDMC Agreement, the Company paid a one-time, upfront fee of $20 thousand, and the Company is responsible for all future patent prosecution costs. The Company recorded the upfront payment as research and development expense in the consolidated statements of operations and comprehensive loss because the acquired technology represented in-process research and development and had no alternative future use. The term of the BIDMC Agreement will

continue until the expiration of the last valid claim within the patent rights covering the licensed products. BIDMC may terminate the agreement in the event (i) the Company fails to pay any amount and fails to cure such failure within 15 days after receipt of notice, (ii) the Company is in material breach of any material provision of the BIDMC Agreement and fails to remedy such breach within 60 days after receipt of notice, or (iii) the Company declares insolvency or bankruptcy. The Company may terminate the BIDMC Agreement at any time upon at least 90 days’ written notice. The Company did not incur any payment obligations under the BIDMC Agreement during the years ended December 31, 2024, 2023 and 2022.

In November 2020, the Company entered into a license agreement (the “DFCI Agreement”) with the Dana Farber Cancer Institute (“DFCI”) pursuant to which the Company obtained a non-exclusive, royalty-bearing license to use, make, have made, develop, market, import, distribute, sell and have sold products covered by patent rights owned by DFCI. Under the terms of the DFCI Agreement, the Company paid a one-time, upfront fee of $25 thousand and approximately $35 thousand for reimbursement of DFCI’s past patent expenses relating to the patent rights. The DFCI Agreement was terminated effective January 20, 2025 and the Company has no further rights or obligations under the DFCI Agreement.

The Company participates in a research and development incentive program provided by the Austrian government whereby the Company is entitled to reimbursement by the Austrian government for a percentage of qualifying research and development expenses incurred by the Company’s subsidiary in Austria. Under the program, the reimbursement rate for qualifying research and development expenses incurred by the Company through X4 Austria is 14% for the current year.

The Company recognizes incentive income from Austrian research and development incentives when qualifying expenses have been incurred, there is reasonable assurance that the payment will be received, and the consideration can be reliably measured. Management has assessed the Company’s research and development activities and expenditures to determine which activities and expenditures are likely to be eligible under the research and development incentive program described above. At each reporting date, management estimates the reimbursable incentive income available to the Company based on available information at the time.

As of the years ended December 31, 2024 and 2023, the amounts due under these programs were $0.7 million and $0.6 million, respectively, which is included in research and development incentive receivable on the consolidated balance sheets. During the years ended December 31, 2024, 2023 and 2022, the Company recorded $0.7 million, $0.6 million and $0.5 million, respectively, of income related to the program on the consolidated statements of operations and comprehensive loss within “other income”.

In July 2019, the Company entered into a license agreement with Abbisko (the “Abbisko Agreement”). Under the terms of the Abbisko Agreement, the Company granted Abbisko the exclusive right to develop, manufacture and commercialize mavorixafor in mainland China, Taiwan, Hong Kong and Macau, the (“Abbisko Territory”). The agreement provides Abbisko with the exclusive rights in the Abbisko Territory to develop and commercialize mavorixafor in combination with checkpoint inhibitors or other agents in multiple oncology indications. The Company retains the full rest-of-world rights to develop and commercialize mavorixafor outside of Greater China for all indications and the ability to utilize data generated pursuant to the Abbisko collaboration for rest-of-world development. Assuming mavorixafor is developed by Abbisko in six indications, the Company would be entitled to milestone payments of up to $214.0 million, which will vary based on the ultimate sales, if any, of the approved licensed products. In addition, upon commercialization of mavorixafor in the Abbisko Territory, the Company is eligible to receive a tiered royalty, with a percentage range in the low double-digits, on net sales of approved licensed products. Abbisko is obligated to use commercially reasonable efforts to develop and commercialize mavorixafor in the Abbisko Territory. Abbisko has responsibility for all activities and costs associated with the further development, manufacture and commercialization of mavorixafor in the Abbisko Territory.

The Company determined that the future sale of clinical and commercial supply are optional goods that will be subject to the customer’s future purchasing decisions and do not represent performance obligations in the Abbisko Agreement. The Company concluded that the amount to be charged for the clinical supply will be reflective of market value and, therefore, the Abbisko Agreement does not provide a discount on such supply that would be accounted for as material right at the outset of the contract. In arriving at these conclusions, the Company considered the complexity of the manufacturing process for the licensed compound and the potential ability for Abbisko to obtain the compound directly from other manufactures in the future. The Company