EAI-045

Targeting lysine residues with covalent inhibitors is challenging due to their abundance in the proteome and the protonation of lysine's ε‐amino group, which diminishes its reactivity. This study introduces diethenyl sulfoximine (DESI) as a novel bio‐orthogonal aminophilic electrophile that can react with lysine via double conjugate addition to form a cyclic adduct. The second addition promotes the entire and efficient electrophilic attack by the ε‐amino of lysine on the ethenyl groups. DESI exhibits superior aqueous stability, overcoming the hydrolysis issue encountered by most reported lysine‐targeting covalent agents. Incorporation of DESI in the allosteric pocket binder EAI045 of oncoprotein epidermal growth factor receptor (EGFR) yields compound 4, which specifically reacts to the catalytic lysine (Lys745). Compound 4 showed potent inhibition of EGFR‐driven cell proliferation with IC50 values of 0.789 µM and 1.22 µM in engineered BaF3‐EGFRL858R/T790M/C797S and NCI‐H1975 cells, respectively, overcoming EAI045's limitation of lack of cellular potency as a single agent. Tyrosine kinases (TKs) panel profiling confirmed selectivity toward mutant EGFR while sparing the wild type with minimal off‐targets. These findings highlight DESI's potential as a versatile strategy for targeting lysine residues irreversibly, offering solutions to overcome drug resistance in cancer therapy and advance next‐generation precision medicines.

The epidermal growth factor receptor (EGFR) family, comprising receptor tyrosine kinases (RTK) such as EGFR and HER2, plays a critical role in various signaling pathways related to cell proliferation, differentiation, and growth. EGFR overactivation due to aberrant signaling can lead to various cancers, including non‐small cell lung cancer (NSCLC). To develop treatment for EGFR‐related NSCLC, several tyrosine kinase inhibitors (TKIs) were designed: gefitinib, erlotinib, as first‐generation; neratinib, dacomitinib as second‐generation; osimertinib, lazertinib as third‐generation, as examples. However, due to the acquired resistance by the mutations such as EGFRT790M and EGFRC797S together with the exon 20 insertion mutations, these drugs do not provide promising results for NSCLC patients. The development of fourth‐generation inhibitors like EAI045 and further innovative drugs to overcome this resistance problem is a must to cure EGFR‐related NSCLC. Among these, pyrazoline‐thiazole scaffolds are found effective as EGFR‐HER2 inhibitors against NSCLC, making them promising drug candidates. Although structures obtained so far for the EGFR family provide meaningful insights into the mechanisms, the quality and the quantity of the EGFR family structures are insufficient to elucidate the complete structures and functions to overcome NSCLC. This review evaluates the structures of EGFR‐HER2 and investigates their relation to NSCLC.