NRP1 and central nervous system cancer: iRGD (CRGDKGPDC) is an RGD-derived peptide consisting of an RGD sequence that binds integrin αγβ3 and a recessive regular (CendR) sequence that binds extravasation and tissue osmosis associated with neuropilin-1 (NRP-1) [33,106], which is a non-tyrosine kinase receptor that exists in excess on the outer surface of glioma cells and angiogenic endothelial cells, with an expression level more than two times that of healthy cells [107,108].