Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2024
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS Norgine Agreement On January 13, 2025, the Company entered into a License and Supply Agreement (the “Norgine Agreement”) with Norgine Pharma UK Limited (“Norgine”), pursuant to which Norgine is granted an exclusive license to (i) distribute, market and sell the Company’s product mavorixafor (marketed by the Company as XOLREMDI in the United States) for all indications in the European Economic Area, Switzerland, the United Kingdom, Australia and New Zealand (collectively, the “Territory”), following regulatory approval. Additionally, Norgine was granted a co-exclusive license to manufacture mavorixafor for the Territory within the Field (as defined in the Norgine Agreement). The Company retains all rights to mavorixafor outside the Territory and specific reserved rights within the Territory. Norgine may grant sublicenses to its affiliates and certain third parties subject to the terms of the Norgine Agreement, except that it may not sublicense the commercial rights granted under the Norgine Agreement for certain countries without X4’s explicit consent. Pursuant to the terms of the Norgine Agreement, the Company shall receive the following payments from Norgine: (i) an upfront payment in the amount of €28.5 million (such payment was received in January 2025), (ii) up to approximately €226.0 million upon the achievement of certain regulatory, commercial and sales milestones, and (iii) escalating double-digit royalties of up to mid-twenties on any future net sales in the Territory. The tiered royalty payments are subject to royalty stacking, and to a material reduction on a country-by-country basis if a generic version of mavorixafor becomes available in the applicable country. X4 and Norgine will collaborate closely on regulatory filings, with X4 continuing to be responsible for the ongoing global, pivotal Phase 3 4WARD clinical trial evaluating mavorixafor in chronic neuropathy. Norgine will be responsible for all market access and commercialization activities and will eventually hold all marketing authorizations in the licensed territories. The Company will manufacture and supply mavorixafor to Norgine. Norgine shall be required to pay a supply price to the Company for the licensed product derived from the CMO costs plus a low double-teen digit of the CMO costs. Subject to customary rights of each party to earlier terminate the Norgine Agreement, the term of the Norgine Agreement continues, on a country-by-country basis, until the later of: (i) the tenth (10th) anniversary of the first commercial sale of mavorixafor, (ii) expiration of regulatory market exclusivity of mavorixafor or (iii) expiration of the last-to-expire licensed patent in such country. The term of the Norgine Agreement shall be automatically renewed for additional three-year terms unless either party provides the other party written notice of its intent not to renew the Agreement at least one year prior to the applicable termination date of the Agreement. In the event of automatic renewal, the royalty payment rate drops to a single digit royalty. Q1 2025 Restructuring On February 6, 2025, the Company announced a strategic restructuring of its workforce and capital spending to focus efforts on advancing mavorixafor to treat those with chronic neutropenia, while also optimizing its U.S. promotion of XOLREMDI. In connection with this shift in operational focus and strategic restructuring, the Company expects to implement a net reduction of its employee headcount by approximately 30% of the Company’s employees. The strategic restructuring activities include (i) discontinuing of research efforts, (ii) closing the Company’s facility in Vienna, Austria, (iii) pausing pre-clinical drug candidate programs, (iv) scaling the U.S. commercial field team and supporting roles across the Company and (v) streamlining other spending to support the ongoing clinical development of mavorixafor for the larger population of those with chronic neutropenia. The Company estimates that the workforce reduction will be substantially completed in the first quarter of 2025.