Covalent Fragments\nActing as Tyrosine Mimics for Mutant\np53-Y220C Rescue by Nucleophilic Aromatic Substitution

The tumor suppressor p53 is frequently mutated in human\ncancers.\nThe Y220C mutant is the ninth most common p53 cancer mutant and is\nclassified as a structural mutant, as it leads to strong thermal destabilization\nand degradation by creating a solvent-accessible hydrophobic cleft.\nTo identify small molecules that thermally stabilize p53, we employed\nDSF to screen S<sub>N</sub>Ar-type electrophiles from our covalent\nfragment library (CovLib) for binding to different structural (Y220C,\nR282W) and DNA contact (R273H) mutants of p53. The reactive fragments\nSN001, SN006, and SN007 were detected to specifically stabilize Y220C,\nindicating the arylation of Cys220 in the mutational cleft, as confirmed\nby X-ray crystallography. The fragments occupy the central cavity\nand mimic the ring system of the WT tyrosine lost by the mutation.\nSurpassing previously reported noncovalent ligands, SN001 stabilized\nT-p53C-Y220C concentration-dependently up to 4.45 °C and, due\nto its small size, represents a promising starting point for optimization.