EGFR and metastatic colorectal cancer: Beside small molecule inhibitors, several antibodies are being clinically developed to target RTKs such as trastuzumab which is used to target the extracellular domain of the HER2 protein in HER2-positive breast cancer patients and has been shown to increase survival at early and late stages of breast cancer [6], and cetuximab used to target the EGFR-ligand binding in the treatment of patients with metastatic colorectal cancer [7].