Lazarus Fragments: Resurrecting Mutants of the Incapacitated Tumor Suppressor p53 by SNAr-based Warheads

The tumor suppressor p53 is frequently mutated in human cancers [1]. The Y220C mutant is the ninth most common p53 cancer mutant and is classified as a structural mutant, as it leads to strong thermal destabilization and degradation, by creating a solvent-accessible hydrophobic cleft [1-3]. To identify small molecules that thermally stabilize p53 [2-4], we employed DSF to screen SNAr-type electrophiles from our covalent fragment library (CovLib) [5] for binding to different structural (Y220C, R282W) and DNA contact (R273H) mutants of p53. The reactive fragments SN001, SN006, and SN007 were detected to specifically stabilize Y220C, indicating arylation of Cys220 in the mutational cleft, as confirmed by X-ray crystallography. The fragments occupy the central cavity and mimic the ring system of the WT tyrosine lost by the mutation. Surpassing previously reported ligands, SN001 stabilized T-p53C-Y220C concentration-dependently up to 4.45 °C and, due to its small size, represents a promising starting point for optimization.