ERBB2 and neoplasm: By constructing ITs containing either a human single-chain antibody (scFv) C6.5 or the murine scFv e23 fused to recombinant gelonin (rGel) molecule, using the flexible G4S linker (L), the fusion construct C6.5-L-rGel was directly compared to e23-L-rGel and specific cytotoxic effects evaluated against Her2/neu-positive and Her2/neu-negative tumor cells.