Pharmacologyreversibly inhibits overall epidermal growth factor receptor (her1/egfr) - tyrosine kinase activity. intracellular phosphorylation is inhibited which prevents further downstream signaling, resulting in cell death. erlotinib has higher binding affinity for egfr exon 19 deletion or exon 21 l858r mutations than for the wild type receptor. indicationsnon-small cell lung cancer, metastatic: treatment of metastatic non-small cell lung cancer (nsclc) in tumors with epidermal growth factor receptor (egfr) exon 19 deletions or exon 21 (l858r) substitution mutations as detected by an approved test either as first-line, maintenance, or as second or greater line treatment after progression following at least 1 prior chemotherapy regimen.limitations of use: use in combination with platinum-based chemotherapy is not recommended. safety and efficacy of treatment for metastatic nsclc with egfr mutations other than exon 19 deletion or exon 21 (l858r) substitution have not been est