In the preclinical studies,a tetravalent antibody, T-Fc, after conjugation with MMAE showed specifictoxicity toward FGFR1 overexpressing cells.55 Protein formats consisting of parts of antibodies can also serveas carriers for the cytotoxic payload, e.g., scFv (single-chain variablefragment), Fab, or diabodies.56−58 scFv fusion with the Fc domainof IgG1 was developed to target FGFR1 and used as a vehicle to deliverMMAE to FGFR1-positive cancer cells,59 aswell as a peptibody (peptide–Fc domain fusion) MMAE conjugatedeveloped by us previously.30 This evidence concerns the gene FGFR1 and cancer.