MSX-122 is also incapable of blocking the binding of 125I-labeled CXCL12 to CXCR4. MSX-122 appears to be insufficiently large to block all binding sites between CXCR4 and CXCL12. MSX-122 blocks certain CXCR4 functions via binding to the CXCL12-binding site and interfering with CXCR4/CXCL12-mediated signaling. MSX-122 can intervene in the Gαi-signaling pathway (cAMP modulation), but not the Gq-pathway (calcium flux).