GPA33 and colorectal cancer: Different types of IMTXs targeted against colorectal cancer and based on α-sarcin have been described and characterized, such as a monomeric GPA33 (glycoprotein A33)-target IMTX, monomeric and trimeric anti-CEA IMTXs [11], and EGFR-targeted IMTXs [12], exhibiting high specificity and potent cytotoxic effects on tumor cells.