Lysine-targeted covalent inhibitors: mechanistic advances, pharmacological perspectives and translational challenges

Targeted covalent inhibitors can provide potent and durable target modulation, but their development has largely centered on cysteine. Lysine offers a complementary covalent handle because it is widely distributed across catalytic sites, ligand-binding pockets, allosteric regions, and protein-protein interaction interfaces. Its high protonation state and proteomic abundance, however, make selective engagement particularly challenging. Recent studies have shown that productive lysine targeting depends less on the intrinsic reactivity of an aminophilic warhead than on molecular recognition, reaction geometry, the local protein environment, and the stability of the resulting adduct. This Review discusses the major chemical strategies used for irreversible, reversible, and conditionally activated lysine targeting, together with representative applications across enzymes, kinases, and protein-protein interaction targets. Particular emphasis is placed on how covalent reaction mechanisms influence target engagement, residence time, cellular persistence, selectivity, and in vivo pharmacology. We also consider the experimental evidence required to distinguish nonspecific or probe-like protein labeling from pharmacologically meaningful covalent inhibition. By integrating warhead chemistry with biochemical mechanism and drug action, this Review highlights the opportunities and remaining challenges in developing lysine-targeted covalent inhibitors as a broader therapeutic modality.