[New type recombinant antibody fragment scFv multimer and cancer targeting]

New type recombinant antibody single chain variable fragment (scFv) is formed by the joined VH and VL domains of immunoglobulin with the used of a polypeptide linker that is at least 12 residues in length. scFv is the smallest functional unit of antibody and has shown a fine prospect for the radioimmunoscintigraphy of cancer because of its special characteristics including increased tumour penetration and fast clearance rates compared with parent Ig. A scFv molecule with a linker of 3-12 residues cannot fold into a functional Fv domain and instead associates with a second scFv molecule to form a bivalent dimer (Diabody). Reducing the linker length below three residues can force scFv association into trimers (Triabody) or tetramers (Tetrabody) depending on linker length, composition and V-domain orientation. This review describes linker length and V-domain orientation of scFv, expression and stability of scFv multimers, size of scFv multimers and its effect on in vivo pharmacokinetics, flexibility and avidity of scFv multimers, in vitro application of multimeric murine scFv, multispecific scFv multimers and cancer targeting.