Design, Synthesis, and Biological Evaluation of Lysine-Stapled Peptide Inhibitors of p53-MDM2/MDMX Interactions with Potent Antitumor Activity .

We introduce novel lysine-stapled peptide inhibitors targeting -MDM2/MDMX interactions. Leveraging the model peptides pDI (LTFEHYWAQLTS) and PMI-M3 (LTFLEYWAQLMQ) as starting points, a series of lysine-stapled analogues were designed and synthesized. Through cell assay screening, two lead compounds, SPDI-48-T and SPMI-48-T, were identified for their excellent antiproliferation activity. Fluorescence polarization assays revealed that both compounds exhibited strong binding affinities against MDM2 and MDMX, ascertained by values within the low micromolar spectrum. Further characterization of SPDI-48-T and SPMI-48-T demonstrated that SPDI-48-T possessed superior cell permeability and serum stability. Notably, SPDI-48-T displayed a dose-dependent suppression of tumor growth in an HCT116 xenograft mouse model. Our findings indicate that SPDI-48-T holds promise as a lead compound for further development as an anticancer agent by modulating -MDM2/MDMX interactions. Additionally, this study also proved that the lysine stapling strategy may serve as a robust approach for generating peptide ligands targeting other protein-protein interactions.