Protein-binding dye proliferation assays in a panel of cell lines with varying EGFR and HER2 expression confirmed the selectivity of neratinib for these receptors with low nanomolar IC50 values (2–3 nM) for HER2-overexpressing cell lines (SKBR3, BT474, and 3T3/neu) and a slightly higher IC50 value for the EGFR-overexpressing epidermoid carcinoma cell line A431 (mean ± SE: 81 ± 9 nM) [48]. This evidence concerns the gene EGFR and squamous cell carcinoma.