Cell-Permeable Peptide Inhibitors of the p53-hDM2 Interaction via Foldamer Helix Mimicry and Bis-Thioether Stapling.

Combining helical foldamers with α-peptides can produce α-helix mimetics with a reduced peptide character and enhanced resistance to proteolysis. Previously, we engineered a hybrid peptide-oligourea sequence replicating the N-terminal α-helical domain of p53 to achieve high affinity binding to hDM2. Here, we further advance this strategy by combining the foldamer approach with side chain cross-linking to create more constrained cell-permeable inhibitors capable of effectively engaging the target within cells. Starting from the crystal structure of the foldamer-hDM2 complex, we identified specific sites suitable for stapling, and generated a small library of macrocyclic foldamer-peptide hybrids. The most promising binders were subsequently optimized for cellular uptake and tested in a cellular assay. We observed that the introduction of a short segment of positively charged residues at the -terminus of the sequence led to inhibitors that exhibited cytotoxic activity independently of p53. In contrast, neutral acetylated peptide-foldamer macrocycles demonstrated activity in a p53-dependent manner.