Cell-Permeable\nPeptide Inhibitors of the p53-hDM2\nInteraction via Foldamer Helix Mimicry and Bis-Thioether Stapling

Combining helical\nfoldamers with α-peptides can\nproduce α-helix\nmimetics with a reduced peptide character and enhanced resistance\nto proteolysis. Previously, we engineered a hybrid peptide-oligourea\nsequence replicating the N-terminal α-helical domain of p53\nto achieve high affinity binding to hDM2. Here, we further advance\nthis strategy by combining the foldamer approach with side chain cross-linking\nto create more constrained cell-permeable inhibitors capable of effectively\nengaging the target within cells. Starting from the crystal structure\nof the foldamer-hDM2 complex, we identified specific sites suitable\nfor stapling, and generated a small library of macrocyclic foldamer-peptide\nhybrids. The most promising binders were subsequently optimized for\ncellular uptake and tested in a cellular assay. We observed that the\nintroduction of a short segment of positively charged residues at\nthe <i>N</i>-terminus of the sequence led to inhibitors\nthat exhibited cytotoxic activity independently of p53. In contrast,\nneutral acetylated peptide-foldamer macrocycles demonstrated activity\nin a p53-dependent manner.