New 111In labeling of IgG: 111In-oxine mediated chelation

Current methods of ¹¹¹In chelate conjugation labeling of antibodies expose the protein to pH 5–6 during ¹¹¹In chelation. These conditions could be detrimental if the antibody is acid labile. We have successfully labeled human IgG via the cyclic anhydride of DPTA and ¹¹¹In-oxyquinoline(oxine). Chelation was achieved at pH 6.9–8.4 and was complete within 1 min at room temperature. The chelation was sensitive to trace metal contamination on labware and in some reagents (including commercial ¹¹¹In-oxine).     

Detection of hepatic metastases from colorectal carcinoma using indium-111 (111In) labeled monoclonal antibody (mAB): MSKCC experience with mAb 111In-C110

Sixteen patients with colorectal carcinoma and a rising serum carcinoembryonic antigen (CEA) level and no evidence of extra-abdominal disease were administered 5 mg of an anti-CEA monoclonal antibody (mAb), C110, labeled with approx. 5 mCi of ¹¹¹In. All patients subsequently underwent exploratory laparotomy, and samples of tumor and normal tissue were obtained. Hepatic lesions (confirmed by histopathology) were visualized as areas of increased radiotracer uptake in 13 of 16 patients. Single photon emission computed tomography (SPECT) considerably aided detection, being positive in two patients with normal planar images. Ten of the 16 patients had positive x-ray computed tomographic (CT) images. The radioimmunodiagnostic study was falsely negative in 3 of 16 patients with subsequently proven hepatic disease, in one of whom CT was also normal. The antibody study was positive in 80% of lesions, thus being, in this small series, significantly more sensitive (P < 0.01) than CT. ¹¹¹In-C110 is a promising monoclonal antibody for the detection of hepatic metastases from colorectal carcinoma; this is the first study to show consistently greater concentration of ¹¹¹In-labeled antibody in hepatic lesions than in surrounding normal hepatic parenchyma.