Updated project metadata. Tyrosine kinase inhibitors (TKIs) are used to treat non-small cell lung cancers (NSCLC) driven by epidermal growth factor receptor (EGFR) mutations in the tyrosine kinase domain (TKD). TKI responses vary across tumors driven by the heterogeneous group of exon 19 deletions and mutations, but the molecular basis for these differences is not understood. We characterized the dynamics of the selected EGFR exon 19 mutants by HDX-MS to study the molecular basis of TKI sensitivity and tolerance.