Although the toxicities of the clinically-approved EGFR- and HER2-targeting moieties used in EGFRxHER2 T-BsAbs (cetuximab and trastuzumab respectively) do not typically overlap and are generally well-tolerated, the potential on-target/off-tumor side effects of EGFRxHER2 T-BsAbs will need to be carefully monitored. The gene discussed is ERBB2; the disease is neoplasm.