ERBB2 and cancer: Small size substance/antibody such as single chain antibody (scFv) or antigen binding fragment (Fab) is one of the choices based on the report that phage-selected anti-HER2 human scFvs improved antibody induced HER2-mediated endocytosis and displayed strong inhibitory activity on the HER2-overexpressing cancer cell lines, though it is still uncertain whether they have anti-tumour activity in vivo.[3]