Pretargeted PROTAC Strategy Enables Precise Tumor Target Degradation via Self-Assembling Peptides

Proteolysis-targeting chimeras (PROTACs) offer a promising approach to degrade traditionally "undruggable" proteins, surpassing limitations of conventional inhibitors. However, current small-molecule PROTACs suffer from poor membrane permeability attributed to large molecular size, along with undesirable off-target toxicity. In this study, leveraging a novel pretargeted strategy, we developed a peptide-based delivery platform to overcome these limitations. Using the PROTAC DT2216 as a model, this pretargeted system integrates the self-assembling peptide TPE-GK-N₃ (targeting tumor integrin α_vβ₃ via RGD and forming surface-adherent nanofibers) and the DT2216-loaded liposome DSPE-PEG₂₀₀₀-DBCO. The N₃-DBCO bioorthogonal pair was designed to facilitate membrane-localized recruitment of DBCO-functionalized liposomes by the azide-bearing peptide, thereby improving tumor-targeted delivery. In vitro, the system (TPE-GK-N₃+DSPE-PEG₂₀₀₀-DBCO@DT2216) showed significantly enhanced target protein Bcl-xL degradation, cytotoxicity, apoptosis induction, and inhibition of cell migration in MDA-MB-231 cells compared to the free DT2216. In vivo, the system demonstrated profound tumor growth suppression (about 65% inhibition) with no obvious toxicity to normal tissues. This study demonstrates a pretargeted peptide strategy for PROTAC delivery, significantly enhancing anticancer efficacy while mitigating systemic toxicity, offering a promising strategy for future PROTAC development.