A Targeted Radiotheranostic Agent for Glioblastoma: [64Cu]Cu-NOTA-TP-c(RGDfK).

Glioblastoma multiforme (GBM) remains one of the most aggressive and treatment-resistant brain tumors, with poor prognosis and limited therapeutic options. Background/

Objectives

Integrin αvβ3, a cell surface receptor overexpressed in GBM, specifically binds to cyclic arginine-glycine-aspartate-D-phenylalanine-lysine (c(RGDfK)) motif, making it a valuable target for tumor-specific delivery and PET imaging. This study explores a novel radiotheranostic agent, [64Cu]Cu-NOTA-TP-c(RGDfK), which combines the imaging and therapeutic capabilities of copper-64 (64Cu) and the cytotoxic activity of a terpyridine-platinum (TP) complex, conjugated to c(RGDfK).

Methods

A robust protocol was developed for the small-scale preparation of NOTA-TP-c(RGDfK). Comparative cellular studies were conducted using U87 MG glioblastoma (GBM) cells and SVG p12 human astrocytes to evaluate the performance of [64Cu]Cu-NOTA-TP-c(RGDfK) relative to [64Cu]Cu-NOTA-c(RGDfK), [64Cu]Cu-NOTA-TP, natCu-NOTA-TP-c(RGDfK), cisplatin, and temozolomide.

Results

64Cu-radiolabeling of NOTA-TP-c(RGDfK) was achieved with >99% radiochemical purity, and competition assays confirmed high binding affinity to integrin αvβ3 (IC50 = 16 ± 8 nM). Cellular uptake, internalization, and retention studies demonstrated significantly higher accumulation of [64Cu]Cu-NOTA-TP-c(RGDfK) in U87 MG cells compared to control compounds, with 38.8 ± 1.8% uptake and 28.0 ± 1.0% internalization at 24 h. Nuclear localization (6.0 ± 0.5%) and stable intracellular retention further support its therapeutic potential for inducing localized DNA damage. Importantly, [64Cu]Cu-NOTA-TP-c(RGDfK) exhibited the highest cytotoxicity in U87 MG cells (IC50 = 10 ± 2 nM at 48 h), while maintaining minimal toxicity in normal SVG p12 astrocytes.

Conclusions

These results highlight [64Cu]Cu-NOTA-TP-c(RGDfK) as a promising targeted radiotheranostic agent for GBM, warranting further preclinical development.