The resulting mutant cell lines were then assessed for sensitivity to TKIs using gefitinib (reversible EGFR-TKI) and afatinib (irreversible EGFR-TKI).... EGFR exon 19 insertions were introduced into Ba/F3 cells to assess oncogenicity and in vitro sensitivity to EGFR TKIs. The Ba/F3 cells transfected with exon 19 insertions were found to be sensitive to both TKIs, similar to Ba/F3 cells harboring the common EGFR exon 19 deletion (E746_A750del) (Figure 2A).