Dual-Chelator conjugates for [⁶⁸Ga]Ga- and [¹⁷⁷Lu]Lu-based PSMA Radiotheranostics

Prostate-specific membrane antigen (PSMA) is highly overexpressed in prostate cancer (PCa) and represents an attractive target for radiotheranostic applications. While conventional approaches often convert PSMA-targeted imaging agents into therapeutic counterparts through chelator substitution, we explored a dual-chelator strategy by integrating HBED-CC and DOTA into the PSMA-093 scaffold. This design generated three dual-chelator conjugates (1-3) capable of supporting the chelation of both diagnostic and therapeutic radionuclides within a single molecular platform. The compounds were successfully radiolabeled with [⁶⁸Ga]Ga³⁺ and [¹⁷⁷Lu]Lu³⁺, and mass spectrometric analysis confirmed site-selective coordination of Ga³⁺ by HBED-CC and Lu³⁺ by DOTA. All conjugates retained high PSMA-binding affinity in vitro, with [⁶⁸Ga]Ga/[¹⁷⁷Lu]Lu-2 and [⁶⁸Ga]Ga/[¹⁷⁷Lu]Lu-3 demonstrating enhanced cellular uptake in 22Rv1-FOLH-oe (PSMA overexpression) cells. In vivo PET/CT imaging and biodistribution studies revealed that [⁶⁸Ga]Ga-2 exhibited favorable pharmacokinetics, including rapid background clearance and improved tumor retention. Importantly, [¹⁷⁷Lu]Lu-2 achieved high tumor uptake, reaching 8.35%ID/g at 24 h post-injection, indicating effective tumor targeting and prolonged retention. These findings support the dual-chelator strategy as a promising platform for the development of next-generation PSMA-targeted radiotheranostic agents. By enabling efficient integration of diagnostic imaging and radionuclide therapy within a single molecule, this approach offers enhanced flexibility for radiopharmaceutical design while preserving favorable biological performance. The dual-chelator concept may facilitate the development of more effective companion diagnostic-therapeutic pairs and contribute to the advancement of precision oncology.