About Us

X4 is focused on restoring healthy immune system function by developing novel therapeutics for the treatment of rare diseases.

Our first-in-class, oral, small molecule therapeutics are antagonists of chemokine receptor CXCR4, which have the potential to treat a broad range of rare diseases, including primary immunodeficiencies (PIs) and cancer. A number of PIs are attributed to the improper trafficking of immune cells related to the CXCR4 receptor and its ligand CXCL12.

X4’s lead product candidate, Mavorixafor (X4P-001), has completed a Phase 2 trial in patients with a rare genetic PI called Warts, Hypogammaglobulinemia, Infections, and Myelokathexis, or WHIM syndrome. X4 plans to initiate a Phase 3 pivotal trial of Mavorixafor in patients with WHIM syndrome. In addition to the initial focus on WHIM syndrome, X4 believes that the biological rationale and available data on Mavorixafor support potential therapeutic benefits across a broad range of PIs, including Severe Congenital Neutropenia and certain lymphomas, such as Waldenstrom Macroglobulinemia.

X4 is also developing X4P-002, a CXCR4 antagonist that has unique properties that the company believes will enable penetration of the blood-brain barrier and provide appropriate therapeutic exposures to treat brain cancers, including glioblastoma multiforme (GBM).

X4 is led by a team with experience in research, development and commercialization of therapies to treat rare diseases, and is located in Cambridge, MA.


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