Enhanced tumor retention and therapeutic potency in radionuclide therapy using GSH-induced self-assembling peptides

Radiolabeled small-molecule drugs hold significant potential for tumor radionuclide therapy (TRT). However, the clinical application of TRT is constrained by the rapid clearance of small molecules from tumor sites and inadequate tumoral radiation sensitivity. To address these limitations, we report an in situ strategy to consume glutathione for assembly that enhances TRT by increasing reactive oxygen species and extending therapeutic time. The probe, [⁶⁴Cu]Cu-DOTA-PEP1-c(RGDyK) ([⁶⁴Cu]Cu-DP1R), was designed with a glutathione-responsive self-assembling polypeptide backbone (PEP1), a DOTA chelator, and an integrin α_vβ₃-targeting moiety. Radiolabeling under optimized conditions yielded a highly stable complex, with radiochemical purity exceeding 95 %. In vivo PET imaging in U87-MG tumor-bearing mice revealed enhanced tumor-specific distribution and extended retention of [⁶⁴Cu]Cu-DP1R compared to [⁶⁴Cu]Cu-DOTA-c(RGDyK) ([⁶⁴Cu]Cu-DR) at 72 h post-injection (6.20 ± 1.61 %ID/g vs. 1.97 ± 0.75 %ID/g, P < 0.01). Enhanced tumor imaging quality and biocompatibility were also observed. Therapeutic evaluation revealed extended survival rates, with the [⁶⁴Cu]Cu-DP1R group achieving a 3.33-times increase over the [⁶⁴Cu]Cu-DR group, while maintaining high biocompatibility without adverse effects on body weight or physiological health. These results highlight the potential of glutathione-responsive self-assembly to extend tumor retention and improve therapeutic outcomes in TRT. By combining the advantages of small peptide-targeting specificity with the prolonged retention of nanostructures, this approach represents a promising strategy to enhance the efficacy and clinical translation of targeted radionuclide therapies.