Another antibody fragment from this time is the 99mTc-labeled anti-CEA Fab fragment arcitumomab (CEA-scan) derived by proteolytic pepsin cleavage from the parental murine antibody IMMU-4, and approved for diagnostic imaging of colorectal cancers (Behr et al. 1995; Moffat Jr et al. 1996). Here, CEACAM5 is linked to colorectal cancer.