PC9-EGFR-Del19-T790M-C797S-KI Cell Line

The EGFR-T790M-C797S mutation cascade epitomizes the ongoing battle against acquired resistance in EGFR-mutant non-small cell lung cancer (NSCLC). Primary activating EGFR mutations (e.g., exon 19 deletions, L858R) are effectively targeted by first- and second-generation tyrosine kinase inhibitors (TKIs). However, the emergence of the T790M ‘gatekeeper’ mutation in exon 20, which increases ATP affinity and sterically hinders drug binding, is the predominant resistance mechanism. The advent of third-generation, covalent EGFR TKIs like osimertinib revolutionized treatment by selectively inhibiting T790M-positive cells while sparing wild-type EGFR.
Despite high efficacy, resistance invariably develops, with the EGFR C797S mutation being a key on-target driver. This tertiary mutation abolishes the covalent binding of osimertinib to the kinase domain by substituting the critical cysteine residue with serine. When C797S occurs in cis with T790M (on the same allele), it confers resistance to all existing ATP-competitive EGFR TKIs, creating a formidable clinical challenge. This sequential evolution highlights the remarkable adaptability of tumors under therapeutic pressure. Current research is intensely focused on developing fourth-generation allosteric inhibitors, bispecific antibodies, and rational combination therapies (e.g., with MET or HER2 inhibitors) to overcome C797S-mediated resistance and extend survival for patients.