A Tight Contact: the Expanding Application of Salicylaldehydes in Lysine-targeting Covalent Drugs

The installation of aldehydes into synthetic protein ligands is an efficient strategy to engage protein lysine residues in remarkably stable iminebonds and augment the compoundaffinity and selectivity for their biological targets. The high frequency of lysine residues in proteins and the reversibility of the covalent ligand-protein bond support the application of aldehyde-bearing ligands, holding promises for their future use as drugs.This reviewhighlights the increasing exploitationof salicylaldehydemodules in various classes of protein binders, aimed at the reversible-covalent engagement of lysine residues.