biostudies-literatureUnknown9(1)Wang YBlueprint MedicinesFourth-generation EGFR tyrosine kinase are in development to overcome common resistance mutations. We performed deep mutational scanning (DMS) of the EGFR kinase domain in the context of L858R by introducing a saturation library of ~17,000 variants into Ba/F3 cells. DMS library-expressing cells were exposed to osimertinib or BLU-945 to identify escape mutations. L718X mutations were enriched across all conditions. BLU-945 specific mutations included K714R, K716T, L718V, T725M, K728E, K754E/N, N771S/T, T783I, Q791L/K, G863S, S895N, K929I, and M971L. A secondary DMS screen combining osimertinib and BLU-945, exclusively enriched for L718X mutations. Clinically, L718X mutations emerged in two patients treated with BLU-945. One patient with baseline EGFR L858R and L718Q mutations experienced eaNPJ precision oncology294https://www.ebi.ac.uk/biostudies/studies/S-EPMC12368022biostudies-literatureDeep mutational scanning reveals EGFR mutations conferring resistance to the 4th-generation EGFR tyrosine kinase inhibitor BLU-945.PMC12368022Papoian GShum ERanieri MMoore XTRDeng JWong KKHao YHollenberg MSherman FPoirier JTTsidilkovski LAbramyan TMSaribekyan HWang YLopez AfalseDeep mutational scanning reveals EGFR mutations conferring resistance to the 4th-generation EGFR tyrosine kinase inhibitor BLU-945.Fourth-generation EGFR tyrosine kinase are in development to overcome common resistance mutations. We performed deep mutational scanning (DMS) of the EGFR kinase domain in the context of L858R by introducing a saturation library of ~17,000 variants into Ba/F3 cells. DMS library-expressing cells were exposed to osimertinib or BLU-945 to identify escape mutations. L718X mutations were enriched across all conditions. BLU-945 specific mutations included K714R, K716T, L718V, T725M, K728E, K754E/N, N771S/T, T783I, Q791L/K, G863S, S895N, K929I, and M971L. A secondary DMS screen combining osimertinib and BLU-945, exclusively enriched for L718X mutations. Clinically, L718X mutations emerged in two patients treated with BLU-945. One patient with baseline EGFR L858R and L718Q mutations experienced ea2025-01-01T00:00:00Z2025 Aug2026-06-03T06:36:19.813Z2026-04-25T03:20:47.993ZS-EPMC123680224083602510.1038/s41698-025-01086-2