Given that osimertinib demonstrates reduced activity against EGFR alterations specific to GBM, particularly extracellular domain mutations and amplifications, compared to the kinase domain mutations found in NSCLC52 (Supplementary Figure S5), our results suggest that osimertinib can achieve sufficient exposures to inhibit kinase domain mutant EGFR, like those observed in NSCLC EGFR; however, these free drug exposures appear inadequate to robustly inhibit the EGFR alterations found in GBM. This evidence concerns the gene EGFR and glioblastoma.