Disrupting aberrant EGFR catalytic trimers reverses T790M gefitinib resistance

Epidermal growth factor receptor (EGFR) mutations drive up to 50% of non-small-cell lung cancers (NSCLC). Although tyrosine kinase inhibitors (TKIs) like gefitinib initially offer substantial clinical benefit, the emergence of acquired, on-target resistance inevitably limits long-term remission. Beyond structural changes that alter ATP-pocket affinity, EGFR oligomerization drives this resistance, though the underlying mechanisms remain unclear. Here we show that progressive, TKI-resistant secondary and tertiary EGFR-mutant variants assemble on the cell surface into higher-order, ligand-free oligomers organized around pathological catalytic trimers. In contrast, gefitinib-sensitive variants assemble into oligomers where the catalytic units remain as canonical dimers, like those found in wild-type oligomers. Genetically disrupting these pathological trimers into dimers via a single-point mutation rewires downstream signaling, decelerates tumor progression, and reverses gefitinib resistance in vivo . Conversely, genetic engineering of dimers into trimers reinstates aggressive tumor growth. These findings expose a structural vulnerability unique to acquired mutations, demonstrating that selectively targeting these pathological intra-oligomer trimers can overcome resistance, and provide a blueprint for protein-protein interface modulation strategies that spare wild-type signaling.