MSX-122 is an orally bioavailable inhibitor of CXCR4 (IC50 = ~10 nM) with potential antineoplastic and antiviral activities. CXCR4 inhibitor MSX-122 binds to the chemokine receptor CXCR4, preventing the binding of stromal derived factor-1 (SDF-1) to the CXCR4 receptor and receptor activation, which may result in decreased tumor cell proliferation and migration.