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, [(64)Cu]Cu-DOTA-PEP1-c(RGDyK) ([(64)Cu]Cu-DP1R), was designed with a glutathione-responsive self-assembling polypeptide backbone (PEP1), a DOTA chelator, and an integrin α(v)β(3)-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 [(64)Cu]Cu-DP1R compared to [(64)Cu]Cu-DOTA-c(RGDyK) ([(64)Cu]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 [(64)Cu]Cu-DP1R group achieving a 3.33-times increase over the [(64)Cu]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.