AZD9291, an irreversible EGFR TKI, overcomes T790M-mediated resistance to EGFR inhibitors in lung cancer

First-generation EGFR tyrosine kinase inhibitors (EGFR TKI) provide significant clinical benefit in patients with advanced EGFR-mutant (EGFRm⁺) non-small cell lung cancer (NSCLC). Patients ultimately develop disease progression, often driven by acquisition of a second T790M EGFR TKI resistance mutation. AZD9291 is a novel oral, potent, and selective thirdgeneration irreversible inhibitor of both EGFRm⁺sensitizing and T790M resistance mutants that spares wild-type EGFR. This mono-anilino-pyrimidine compound is structurally distinct from other third-generation EGFR TKIs and offers a pharmacologically differentiated profile from earlier generation EGFR TKIs. Preclinically, the drug potently inhibits signaling pathways and cellular growth in both EGFRm⁺and EGFRm/T790M⁺mutant cell lines in vitro, with lower activity against wild-type EGFR lines, translating into profound and sustained tumor regression in EGFR-mutant tumor xenograft and transgenic models. The treatment of 2 patients with advanced EGFRm⁺T790M⁺NSCLC is described as proof of principle. We report the development of a novel structurally distinct third-generation EGFR TKI, AZD9291, that irreversibly and selectively targets both sensitizing and resistant T790M⁺ mutant EGFR while harboring less activity toward wild-type EGFR. AZD9291 is showing promising responses in a phase I trial even at the first-dose level, with first published clinical proof-of-principle validation being presented.