ERBB2 and head and neck squamous cell carcinoma: We compare the efficacy of T‐DXd, trastuzumab‐emtansine (ADC comprising an anti‐HER2 antibody and microtubule inhibitor, T‐DM1; Kadcyla) and trastuzumab (Herceptin) therapy in HNSCC with low and absent HER2 expression in vitro and in vivo.