Melanoma targeting property of a Lu-177-labeled lactam bridge-cyclized alpha-MSH peptide

The purpose of this study was to determine the melanoma targeting property of ¹⁷⁷Lu-DOTA-GGNle-CycMSH_hex in B16/F1 melanoma-bearing C57 mice. ¹⁷⁷Lu-DOTA-GGNle-CycMSH_hex exhibited high receptor-mediated melanoma uptake and fast urinary clearance. The tumor uptake of ¹⁷⁷Lu-DOTA-GGNle-CycMSH_hex was 20.25 ± 4.59 and 21.63 ± 6.27% ID/g at 0.5 and 2 h post-injection, respectively. Approximately 83% of injected dose cleared out the body via urinary system at 2 h post-injection. ¹⁷⁷Lu-DOTA-GGNle-CycMSH_hex showed high tumor to normal organ uptake ratios except for the kidneys. The tumor/kidney uptake ratios of ¹⁷⁷Lu-DOTA-GGNle-CycMSH_hex were 2.76 and 1.74 at 2 and 24 h post-injection. The melanoma lesions were clearly visualized by SPECT/CT using ¹⁷⁷Lu-DOTA-GGNle-CycMSH_hex as an imaging probe at 2 h post-injection. Overall, high melanoma uptake coupled with fast urinary clearance of ¹⁷⁷Lu-DOTA-GGNle-CycMSH_hex underscored its potential for melanoma treatment in the future.