In vitro and in vivo comparison of binding of 99m-Tc-labeled anti-CEA MAb F33-104 with 99m-Tc-labeled anti-CEA MAb BW431/26

Aim: The purpose of this study was to assess the potential for radioimmunod etection (RAID) of murine anti-carcinoembryonic antigen (CEA) monoclonal an tibody (MAb) F33-104 labeled with technetium-gsm (99m-Tc) by a reduction-me diated labeling method. Methods: The binding capacity of 99m-Tc-labeled ant i-CEA MAb F33-104 with CEA by means of in vitro procedures such as immunora diometric assay and cell binding assay and the biodistribution of 99m-Tc-la beled anti-CEA MAb F33-104 in normal nude mice and nude mice bearing human colon adenocarcinoma LS180 tumor were investigated and compared with 9gm-Tc -labeled anti-CEA MAb BW431/26. Results: The in vitro binding rate of 99m-T c-labeled anti-CEA MAb F33-104 with CEA in solution and attached to the cel l membrane was significantly higher than 99m-Tc-labeled anti-CEA MAb BW431/ 261 (31.4 +/- 0.95% vs. 11.9 +/- 0.55% at 100 ng/mL of soluble CEA, 83.5 +/ - 2.84% vs. 54.0 +/- 2.54% at 10(7) of LS 180 cells). In vivo, accumulation of 99m-Tc-labeled anti-CEA MAb F33-104 was higher at 18 h postinjection th an 99m-Tc-labeled anti-CEA MAb BW431/26 (20.1 +/- 3.50% ID/g vs. 14.4 +/- 3 .30% ID/g). 99m-Tc-activity in the kidneys of nude mice bearing tumor was h igher at 18 h postinjection than at 3 h (12.8 +/- 2.10% ID/g vs. 8.01 +/- 2 .40% ID/g of 99m-Tc-labeled anti-CEA MAb F33-104, 10.7 +/- 1.70% ID/g vs. 8 .10 +/- 1.75% ID/g of 99m-Tc-labeled anti-CEA MAb BW431/26). Conclusion: 99 m-Tc-labeled anti-CEA MAb F33-104 is a potential novel agent for RAID of re current colorectal cancer.