Ramucirumab (anti-VEGFR2)

Ramucirumab is direct inhibitor of VEGF-R2, where it binds to the extracellular VEGF-binding domain with high degree of specificity and affinity, at picomolar dose range. It thus prevents the binding of the VEGF ligand to the VEGF-R2 receptor. Ramucirumab has potential advantages over bevacizumab as it is selective for VEGF-R2, whereas bevacizumab by targeting VEGF-A affects VEGF-R1, -R2, and the noncatalytic coreceptors neuropilin-1and -2^[1]. Ramucirumab prevents the binding of VEGFR ligands: VEGF-A, VEGF-C, and VEGF-D to its receptors. Thus, ramucirumab inhibits the angiogenesis pathways involved in the development and progression of gastric cancer^[2]. ramucirumab demonstrates inhibition of VEGF-stimulated VEGFR-2 activation, proliferation of human endothelial cells, VEGF migration of human leukemia cells, and VEGF induced phosphorylation of VEGFR-2 in human umbilical vein and porcine aortic endothelial cells overexpressing VEGFR-2^[3]. Preclinical in vitro data revealed that ramucirumab has a high affinity for VEGFR-2, showing a half-maximal effective concentration (EC50) of 0.15 nM, 8- to 9-fold higher than its natural ligand VEGFA. Ramucirumab binds VEGFR-2 in domain 3 near the N-terminus, both as a soluble protein and as a cell-surface receptor, with a IC50 of 1-2 nM^[4].

The anti-KDR antibodies were added to the microwells of a 96-well plate coated with KDR(Ig1-7) (full-length KDR ECD), KDR(Ig1-3) (variant that contains only the first three N-terminal Ig domains of KDR ECD), or KDR(Ig1) (variant that contains only the first N-terminal Ig domain of KDR ECD) and incubated at room temperature for 1 h. The plate was washed and then incubated with a mouse anti-human Fc antibody-HRP conjugate for additional 1 h, after which the plate was developed as described above. Antibody binding to the two Ig deletion variants are shown as relative (as percentages) to their binding to the full-length KDR ECD.