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 Pharmaceutical’s lead product candidate, mavorixafor (X4P-001), is a potentially first-in-class, once-daily, oral inhibitor of CXCR4, currently in Phase 3 development for the treatment of WHIM syndrome, a rare, inherited, primary immunodeficiency disease caused by genetic mutations in the CXCR4 receptor gene. Mavorixafor has demonstrated proof of concept in WHIM in a Phase 2 trial, including clinically meaningful increases in neutrophil and lymphocyte biomarker counts, as well as a trend of reduction in infection rates and wart burden, and a favorable safety profile. A Phase 2 open label extension study for WHIM is ongoing. Mavorixafor was designated orphan drug status by the U.S. Food and Drug Administration in 2018 for the treatment of WHIM and is also in development for Severe Congenital Neutropenia (SCN), Waldenström’s macroglobulinemia (WM), and clear cell renal cell carcinoma (ccRCC).

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. The company is located in Cambridge, MA with research offices based in Vienna, Austria.

 

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