Comparison of Seven Iodine-Labelled Monoclonal Antibodies in Nude Mice with Human Colon Carcinoma Xenografts

Abstract

The biokinetics of seven ¹³¹I-labelled monoclonal antibodies (MAbs), directed against human colon carcinoma and one ¹²⁵I-labelled unspecific MAb have been examined. the study in nude mice, carrying human colon carcinoma, was intended to be a step in the selection of the most suitable antibody for clinical scintigraphy. the biological half-life in blood was found to be between 1.3 and 7.4 days for the different MAbs. Chromatography of plasma samples showed that the radioiodine was mainly bound to IgG-sized molecules. the (normal tissue)/blood ratios were similar for all the MAbs. the tumour/blood ratio was 0.41 for the unspecific MAb and 0.49-1.1 for the specific MAbs, and the tumour/muscle ratio was between 3.2 and 6.8 for the specific MAbs 6 days after injection. for one MAb tumour/blood and tumour/muscle ratios were 3.9 and 9.8 respectively 9 days after injection. Localization indices were at their highest 2.6 6 days after injection. for at least two of the monoclonal antibodies the tumour/blood and tumour/ muscle ratios found are high enough to justify clinical trials regarding their usefulness for scintigraphy of colon cancer in man.