Establishment and validation of an alternative automated synthesis of [68Ga]Ga-DOTA-Siglec-9 in an independent laboratory for clinical use.

BACKGROUND: Siglec-9, a member of the Siglec family of receptors, plays a crucial role in modulating immune cell trafficking and inflammation, with significant clinical implications. It is predominantly expressed on immune cells such as neutrophils, monocytes, and dendritic cells -key components of both innate and adaptive immunity. Siglec-9 binds to sialic acid residues on glycoproteins, commonly found on endothelial cells, a mechanism central to immune regulation during inflammation and tissue injury. Notably, its interaction with vascular adhesion protein 1 (VAP-1), an endothelial adhesion molecule, is of particular interest for therapeutic development in chronic inflammatory diseases, autoimmune disorders, and cancer. Recent studies have demonstrated that a Siglec-9 motif-containing peptide conjugated with 1,4,7,10-tetraazacyclododecane-N, N',N'',N'''-tetraacetic acid (DOTA) and radiolabelled with gallium-68 ([⁶⁸Ga]Ga-DOTA-Siglec-9) enables effective positron emission tomography (PET) imaging of these pathological conditions. This study aimed to develop a new automated radiolabelling protocol for the preparation of [⁶⁸Ga]Ga-DOTA-Siglec-9 for clinical use. The synthesis was carried out using a fully automated module with real-time monitoring of key parameters including time, temperature, and radioactivity. RESULTS: Following optimization of labelling conditions and assessment of peptide stability, [⁶⁸Ga]Ga-DOTA-Siglec-9 was successfully synthesized with a radiochemical yield (RY) of 55.04%, radiochemical purity (RCP) of 99.48%, and molar activity (Am) of 23.15 GBq/µmol at 65 °C in 6 min. Process validation yielded consistent mean values of RY (56.16%), RCP (99.40%). and Am (20.26 GBq/µmol). Stability testing at room temperature over 3 h demonstrated that [⁶⁸Ga]Ga-DOTA-Siglec-9 maintained acceptable RCP (mean99.29%), pH, appearance, and sterility. CONCLUSION: The final product meets Ph. Eur. quality requirements and is suitable for clinical application.