Pharmacokinetics of an indium-111-labeled monoclonal antibody in cancer patients.

The authors have evaluated the pharmacokinetics in patients of a monoclonal antibody (19-9) F(ab')/sub 2/ fragment coupled with DTPA and labeled with /sup 111/In. In addition to imaging and organ uptake determinations, serum and urine samples were analyzed to help determine the in vivo behavior of the label. Using a competitive binding assay, the immunoreactivity of the coupled fragment was found to be indistinguishable from that of the unmodified fragment. By a variety of techniques, they show that the only significant source of label instability was transcomplexation to circulating transferrin. Whole-body clearance of the label was slow and may be attributed entirely to urinary excretion. Organ accumulation was greatest in the liver and persisted after rapidly attaining high values. A total of 14 cancer patients were studied, nine with identifiable sites of metastatic disease from colorectal, pancreatic, ovarian, or small cell lung primaries. Eight of the 12 sites of documented tumor were visualized by external imaging (67%) most distinctly at 48-72 hr postadministration.