AKB-6899 is an inhibitor of prolyl hydroxylase domain 3 (PHD3) and increases the soluble form of the VEGF receptor (sVEGFR-1) production from GM-CSF-treated macrophages. AKB-6899 leads to stabilization of HIF-2α which induces sVEGFR-1 production from tumor-associated macrophages and decreases tumor growth.