Synthesis, radiolabelling and preliminary evaluation of [⁶⁸Ga]Ga-DOTA-linked cyanuric chloride-glu-ureido scaffold for PSMA PET imaging

Cyanuric chloride is a highly reactive, widely recognized compound in medicinal chemistry, enabling rapid and selective nucleophilic substitution reactions at its three chlorine positions. In the present study, explore the structural advantages of cyanuric chloride to develop a new DOTA-linked triazine-based scaffold for PSMA. Two scaffolds, abbreviated as PSMA-C1D and PSMA-C2D, were successfully synthesized with good yields and evaluated their properties through molecular docking, in vitro studies, radiolabelling, physicochemical properties, and internalization studies. The initial screening revealed that, the PSMA-C1D had greater potential as a PSMA-targeted imaging agent than PSMA-C2D. In vitro cytotoxicity assays further indicated good biocompatibility at imaging-relevant concentrations. The molecular docking demonstrated strong site-specific binding of PSMA-C1D to the PSMA active pocket (ΔG = - 10.2 kcal/mol), with interactions closely resembling the co-crystallized ligand. The radiolabelling of PSMA-C1D with Ga-68 shows high yield with > 95% radiochemical purity, excellent stability in multiple biological media, and high apparent molar activity (508 GBq/µmol). The tracer shows hydrophilicity (logD_7.4 = - 2.76 ± 0.02), low %PPB (18 ± 5.4), and has a nanomolar affinity (K_d = 0.38 nM), with the percentage of bound internalization in LNCaP cells was 15 ± 2.9% incubation for 1 h. The study highlights the value of cyanuric chloride as a modular chemical hub for the design and linking of radiopharmaceuticals. It identifies [⁶⁸Ga]Ga-PSMA-C1D as a promising, efficiently synthesizable, and highly PSMA-specific PET radiotracer for imaging prostate cancer.