X4 Pharmaceuticals is a clinical-stage biopharmaceutical company focused on rare blood disorders, built around a single asset: mavorixafor (XOLREMDI), an oral, once-daily CXCR4 receptor blocker that mobilizes white blood cells from bone marrow into the bloodstream. XOLREMDI is FDA-approved for WHIM syndrome, an ultra-rare inherited immunodeficiency affecting roughly 1,000 diagnosed U.S. patients, making it the first approved therapy for the condition. X4 sells XOLREMDI in the U.S. directly through a specialty pharmacy, and has licensed ex-U.S. commercial rights to regional partners: Norgine covers Europe, Australia, and New Zealand; taiba rare covers select MENA countries; and Abbisko covers Greater China. The Norgine deal included a €28.5M upfront payment and up to €226M in milestones plus tiered royalties. The larger strategic bet is chronic neutropenia (CN), a rare blood disorder affecting an estimated 57,000 diagnosed U.S. patients, where the current standard of care is injectable G-CSF therapy. X4 is running the Phase 3 4WARD trial targeting full enrollment in Q3 2026 and top-line data in the second half of 2027, with potential FDA approval in 2028. X4 positions mavorixafor as an oral alternative or combination partner to G-CSF. X4 is pre-profitability, funds operations through equity raises, and executed significant cost cuts in 2025, including a roughly 65% headcount reduction, to extend runway while the 4WARD trial completes. X4 in-licenses its core IP from Genzyme and owes royalties of 6–12% on U.S. net sales.