Research progress on covalent inhibitors targeting alkaline amino acids

Over the past two decades, covalent inhibitors have undergone a remarkable resurgence in drug discovery. Currently, targeting non-catalytic cysteine residues with acrylamide and other α,β-unsaturated carbonyl compounds is a predominate strategy, especially in the protein kinase field. Several cysteine-targeting covalent inhibitors (e.g. Ibrutinib, Afatinib) have demonstrated significant clinical efficacy. Covalent inhibitors have also enabled targeting of traditionally undruggable targets, highlighting the unique advantages of covalent strategies over non-covalent ligands. The rapid recent development of covalent strategies has prompted researchers to make significant efforts to develop novel reversible and irreversible covalent binding warheads targeting non-cysteine residues, thereby opening up new chemical space for covalent strategies. This article reviews the research advancements in specific and promiscuous warheads, as well as their covalent ligands, targeting three alkaline amino acids (lysine, arginine, and histidine), which will provide more opportunities for covalent fragment approaches targeting residues beyond cysteine.