A potential new radiopharmaceutical for parathyroid imaging: radiolabeled parathyroid-specific monoclonal antibody--II. Comparison of 125I- and 111In-labeled antibodies.

Abstract The biodistributions of 111 In-BB5-G1 and 111 In-F(ab′) 2 were compared with the biodistributions of the corresponding 125 I-labeled molecules. For BB5-G1 intact antibody, the relative uptake of the 111 In- and 125 I-labeled molecules in human parathyroid tissue implants was similar at 24 h, but by 96 h the uptake of the 111 In-BB5-G1 %ID/g was four times greater than that observed with the 125 I-labeled antibody. For the F(ab′) 2 fragments, the relative parathyroid uptake of the two preparations was similar at all times tested. The uptake by the clearance organs was significantly higher when the 111 In-labeled molecules were used. Imaging results suggest that 111 In-BB5-G1 or 111 In-F(ab′) 2 may be a useful radiopharmaceutical for parathyroid radioimmunodetection.