X4 Pharmaceuticals Inc. is a biopharmaceutical company focused on the research, development, and commercialization of novel therapeutics targeting rare diseases of the immune system and rare hematology diseases. Its lead product, XOLREMDI (mavorixafor), is an orally bioavailable selective antagonist of the chemokine receptor CXCR4, approved in the United States for treating patients with warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome by mobilizing functional white blood cells from the bone marrow into circulation. The company is advancing mavorixafor in the ongoing Phase 3 4WARD clinical trial, evaluating its efficacy, safety, and tolerability, with or without G-CSF, in patients with congenital, acquired primary autoimmune, or idiopathic chronic neutropenia who suffer recurrent or serious infections. X4 Pharmaceuticals Inc. leverages expertise in CXCR4 pathway biology to address unmet needs in conditions characterized by low neutrophil counts and heightened infection risks. Headquartered in Boston, Massachusetts, the company maintains license agreements for mavorixafor development in oncology combinations and specific geographic regions outside the U.S.