The development of ideal peptide-based radiopharmaceuticals faces critical bottlenecks, primarily due to limited cellular internalization and insufficient deep tissue penetration of peptide carriers. To address this, we developed an intracellular targeting and DNA-adjacent radiotherapeutic strategy using stapled peptides. The MDM2/MDMX-targeting stapled peptide-based radiopharmaceuticals, denoted as [64Cu]Cu-DOTA-STP, exhibited prolonged circulation in the bloodstream and slow systemic clearance. Furthermore, in vitro studies demonstrated that nearly 50% of administered [64Cu]Cu-DOTA-STP was internalized, achieving efficient intracellular accumulation. In addition, [64Cu]Cu-DOTA-STP demonstrated high tumor accumulation, with a standard uptake value of up to 9.39 ± 1.52%ID/g. Finally, targeted radionuclide therapy confirmed that [64Cu]Cu-DOTA-STP effectively inhibited tumor growth, irrespective of p53 phenotypes. Taken together, this study leveraged PET imaging as a noninvasive and longitudinal tool to elucidate the in vivo fate of stapled peptides and demonstrated that stapled peptides can serve as ideal vehicles for developing intracellular protein-targeting radiopharmaceuticals, achieving efficient 64Cu-based targeted radionuclide therapy.
Murine double minute 2 (MDM2) and homologous protein murine double minute X (MDMX) are p53 negative regulators that perform significant driving effects in tumorigenesis, and targeting these oncoproteins has became an efficient strategy in treating cancers. However, the definite antitumor activity and significance ordering of each protein in MDM family is still unclear due to the similar structure and complicated regulation. Herein, we identified two G-rich sequences ( G 1 and G 5 ) located in the promoter that could assemble the G-quadruplex to respectively inhibit and promote the transcription of the MDM2 and MDMX. Based on this target, we designed and synthesized a novel G-quadruplex ligand A3f and achieved the differentiated regulation of MDM protein. In triple-negative breast cancer (TNBC) cells, A3f could induce MDM2-dependent proliferation arrest and exhibit additive therapeutic effect with MDMX inhibitors. Overall, this study provided a novel strategy to regulate the transcription of MDM genes by targeting certain G-rich sequences, and discovered an active antitumor molecule for use in TNBC treatment.
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