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 N-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.