177 Lu-Labeled Bivalent Ligands of Prostate-Specific Membrane Antigen for Endoradiotherapy of Prostate Cancer.

Recently, we developed a bivalent prostate-specific membrane antigen (PSMA) radioligand ([ 18 F]AlF-Bi-PSMA), which showed higher tumor uptake and retention in PSMA-positive mouse models than the clinically used radioligands, [ 68 Ga]Ga-PSMA-11 and [ 18 F]PSMA-1007. Here, we developed two 177 Lu-labeled bivalent PSMA ligands with (DOTA-Alb-Bi-PSMA) or without an albumin-binding motif (DOTA-Bi-PSMA) to enhance radiotherapeutic efficacy with minimal toxicity. The results demonstrated that both 177 Lu-labeled bivalent radioligands showed good stability, high binding affinity, and PSMA-targeting specificity in vitro. Compared with [ 177 Lu]Lu-PSMA-617, both [ 177 Lu]Lu-Bi-PSMA and [ 177 Lu]Lu-Alb-Bi-PSMA showed a higher area under the curve (AUC) of tumor accumulation and superior therapeutic efficacy. However, [ 177 Lu]Lu-Alb-Bi-PSMA exhibited a dose-dependent increase in acute damage to kidneys. In terms of the radionuclide therapy efficacy and side effects, [ 177 Lu]Lu-Bi-PSMA exhibited well-balanced action with high tumor-to-organs AUC ratios, resulting in remarkable therapeutic efficacy and negligible side effects. These promising results warrant further investigations to achieve the clinical translation of [ 177 Lu]Lu-Bi-PSMA.