They specifically neutralize the activity of vascular endothelial growth factor (VEGF) or other molecular factors belonging to the VEGF family. Another class of drugs (tyrosine-kinase inhibitors) blocks the kinase activity of VEGF receptor’s family. They are however generally not specific as they interfere with the activity of other tyrosine kinase receptors. Biological drugs for cancer therapy are intravenously administered, intravitreal injections are required to treat eye diseases.