The four cell lines demonstrated varied responses to erlotinib treatment, with an IC50 of 0.27 μM for JHU-011, 7.9 μM for JHU-013, 0.23 μM for JHU-022, and 43 μM for JHU-029, respectively (Supplementary Figure S1), suggesting that, while the HNSCC cells only respond to erlotinib at a micromolar scale, they are exquisitely sensitive to the EGFR-targeting hDT806 at a nanomolar scale. The gene discussed is EGFR; the disease is head and neck squamous cell carcinoma.