Viability of (A) EGFR L858R and (B) EGFR L858M/L861Q Ba/F3 cells after 72 hours of treatment with gefinitib, osimertinib, and afatinib, detected by MTS assay. Error bars represent standard error of the mean. (C) Immunoblotting of lysates from EGFR L858R and EGFR L858M/L861Q NIH-3T3 cells treated with the indicated concentrations of gefitinib, osimertinib, or afatinib. The ratio of phospho-EGFR in treated vs. untreated samples was quantified by densitometry for each cell line.