X4 Pharmaceuticals, Inc., a late-stage clinical biopharmaceutical company, focuses on the research, development, and commercialization of novel therapeutics for the treatment of rare diseases.

Its lead product candidate is mavorixafor, a small molecule inhibitor of the chemokine receptor C-X-C chemokine receptor type 4 (CXCR4), which is in Phase III clinical trial for the treatment of patients with warts, hypogammaglobulinemia, infections, and myelokathexis syndrome; and Phase Ib clinical trial to treat chronic neutropenia and Waldenström macroglobulinemia.

The company is also developing X4P-002, a CXCR4 antagonist for the treatment of brain cancers; and X4P-003, a CXCR4 antagonist for the treatment of CXCR4 disorders and primary immunodeficiencies.

It has a license agreement with Abbisko Therapeutics Co., Ltd. to develop, manufacture, and commercialize mavorixafor in combination with checkpoint inhibitors or other agents in oncology indications.

The company was founded in 2010 and is headquartered in Boston, Massachusetts.