We therefore performed a preclinical study of combined VEGF and CXCR4 antagonism in an intracranial xenograft model of GBM using the Protein Epitope Mimetic (PEM) CXCR4 antagonist POL5551 [34], together with mcr89, an anti-VEGF antibody with dual functionality against both murine and human VEGF [35]. Here, CXCR4 is linked to glioblastoma.