In an effort to utilize EGFR overexpression in HNSCC as a drug development target, we previously engineered a bispecific and bivalent immunotoxin28, DT390-HuBiscFv806, abbreviated as hDT806, targeting the tumor-specific overexpressed EGFR and/or EGFRvIII mutant. The gene discussed is EGFR; the disease is head and neck squamous cell carcinoma.