EGFR and neoplasm: In addition, the benefit of most novel treatment options is conditional on the presence of specific tumor biomarkers associated with response (e.g. expression of programmed death ligand 1 [PD-L1], or particular gene mutations or rearrangements).[2] Erlotinib is an oral highly potent reversible tyrosine kinase inhibitor (TKI) that targets the Human Epidermal Growth Factor Receptor Type 1 (HER1)/Epidermal Growth Factor Receptor (EGFR).