In Vitro: H3255 cells expressing L858R EGFR treated with Gefitinib-based PROTAC 3 (25 nM-10 μM; 24 hours), HCC827 cells expressing exon 19 del EGFR treated with Gefitinib-based PROTAC 3 (100 nM-10 μM; 24 hours), which enables the degradation of both exon-19 deletion EGFR as well as the mutant isoform containing the L858R activating point mutation, while sparing the WT EGFR.