Biological comparison of 149Pm-, 166Ho-, and 177Lu-DOTA-biotin pretargeted by CC49 scFv-streptavidin fusion protein in xenograft-bearing nude mice

Abstract The radiolanthanides 149 Pm, 166 Ho, and 177 Lu possess a range of half-lives and α − β − energies for targeted radiotherapy of cancer. 149 Pm-, 166 Ho-, and 177 Lu-DOTA-biotin were pretargeted to LS174T colorectal tumors in nude mice with CC49 scFvSA antibody-streptavidin fusion protein. Tumor uptakes of 149 Pm (22.9% ID/g), 166 Ho (30.2% ID/g), and 177 Lu (35.4% ID/g) peaked at 1-4 h. Rapid blood disappearance was accompanied by urinary excretion of 59-66% ID within 1 h. Biodistributions of these agents show promise for pretargeted radioimmunotherapy of cancer.