Kinase Inhibition via Small Molecule‐Induced Intramolecular Protein Cross‐Linking

Remarkable progress has been made in the development of cysteine‐targeted covalent inhibitors. In kinase drug discovery, covalent inhibitors capable of targeting other nucleophilic residues (i.e. lysine, or K) has emerged in recent years. Besides a highly conserved catalytic lysine, almost all human protein kinases possess an equally conserved glutamate/aspartate (e.g. E/D) that forms a K‐E/D salt bridge within the enzyme active‐site. Electrophilic ynamides were previously used as effective peptide coupling reagents and to develop E/D‐targeting covalent protein inhibitors/probes. In the present study, we report the first ynamide‐based small‐molecule inhibitors capable of inducing intramolecular cross‐linking of various protein kinases, leading to subsequent irreversible inhibition of kinase activity. Our strategy took advantage of the close distance between the highly conserved catalytic K and E/D residues in a targeted kinase, thus providing a conceptually general approach to achieve irreversible kinase inhibition with high specificity and desirable cellular potency. Finally, this ynamide‐facilitated, ligand‐induced mechanism leading to intramolecular kinase cross‐linking and inhibition was unequivocally established by using recombinant ABL kinase as a representative.