Plerixafor inhibits CXCL12-mediated chemotaxis with a potency slightly better than its affinity for CXCR4.Plerixafor also antagonizes SDF-1/CXCL12 ligand binding with an IC50 of 651 nM. Plerixafor inhibits SDF-1 mediated GTP-binding, SDF-1 mediated calcium flux and SDF-1 stimulated chemotaxis with IC50 of 27 nM, 572 nM and 51 nM, respectively. Plerixafor does not inhibit calcium flux against cells expressing CXCR3, CCR1, CCR2b, CCR4, CCR5 or CCR7 when stimulated with their cognate ligands, Nor does Plerixafor inhibit receptor binding of LTB4. Plerixafor does not, on its own, induce a calcium flux in the CCRF CCEM cells, which express multiple GPCRs including CXCR4, CCR4 and CCR7