Definition

The hydrobromide salt form of burixafor, an orally bioavailable inhibitor of CXC chemokine receptor 4 (CXCR4) with hematopoietic stem cell (HSC)-mobilization and chemosensitizing activities. Upon administration, burixafor binds to the chemokine receptor CXCR4, thereby preventing the binding of stromal cell-derived factor-1 (SDF-1 or CXCL12) to the CXCR4 receptor and subsequent receptor activation. This may induce the mobilization of hematopoietic stem and progenitor cells from the bone marrow into the peripheral circulation. Additionally, burixafor-mediated mobilization of disseminated tumor cells (DTCs) from the bone marrow into the blood may make these metastatic tumor cells more susceptible to the actions of chemotherapeutic agents. CXCR4, a chemokine receptor belonging to the G protein-coupled receptor (GPCR) gene family, plays an important role in chemotaxis and angiogenesis and is upregulated in several tumor cell types. CXCL12/CXCR4 interaction induces retention of hematopoietic cells in the bone marrow.