ESR2 and neoplasm: This new immunoconjugate, called anti-ErbB2 human compact antibody-RNase (Erb-hcAb-RNase), has shown to fully retain the binding ability, ADCC and CDC properties of Erb-hcAb and to acquire the RNase activity of its enzymatic moiety, thus inhibiting tumour cell proliferation in vitro and in vivo more efficiently than the parental Erb-hcAb.