ERBB2 and neoplasm: While such adverse effects have not been definitively observed in current preclinical or clinical studies, lessons from CAR‐T cell therapies against other antigens (e.g., CAIX, HER2, EGFR) highlight the potential for severe or irreversible off‐tumour toxicity when targeting antigens with low‐level normal tissue expression, underscoring the need for careful safety evaluation and long‐term monitoring.157