Pharmacokinetics of the FO23C5 anti-CEA antibody fragment labelled with 99Tcm and 111In

Publisher Website
Google Scholar
Abstract
The FO23C5 anti-carcinoembryonic antigen (CEA) F(ab')2 antibody was radiolabelled with 111In via diethylenetriaminepentaacetic acid (DTPA) and directly with 99Tcm by stannous ion and mercaptoethanol antibody reduction to compare the pharmacokinetics of these three agents. Four patients received 15 mCi 99Tcm-Fab' 1 week before receiving 1 mCi 111In-F(ab')2. Five additional patients received only the 99Tcm-Fab'. Radiochromatograms by high-performance liquid chromatographic (HPLC) analysis of serum and urine samples from patients receiving 111In were typical of those observed by us previously in connection with other antibodies. The identical analyses of samples from patients receiving 99Tcm showed no differences with the method of reduction and more complex radiochromatograms. In addition to peaks due to a mixture of labelled F(ab')2 and Fab' fragments and, occasionally, immune complexes, there were several peaks due to labelled cysteine and other small labelled species present in both serum and urine. The biodistribution of 99Tcm was as expected for a labelled Fab' fragment: relative to 111In, 99Tcm cleared rapidly from circulation and into kidneys and urine. Liver levels of 111In and 99Tcm were surprisingly similar at 1 day (12 versus 9% ID) although initial 111In levels were lower and increased while 99Tcm levels were higher and decreased. Spleen levels were also similar. In 4/9 patients receiving 99Tcm, hepatobiliary clearance was observed at levels which could confuse interpretation whereas this mode of clearance was observed in only 1/4 patients receiving 111In. Image quality was superior with 111In versus 99Tcm at 1 day postadministration as judged by counting rates and background activity whereas the opposite was true at 2-3 h postadministration.

This publication has 0 references indexed in Scilit: