To test the hypothesis that bispecific targeting will increase tumour-targeting selectivity of antibody-based agents, we took advantage of two previously identified scFv, the anti-ErbB2 ML3.9 scFv (Schier et al, 1996) and the anti-ErbB3 A5 scFv (Horak et al, 2005). Here, ERBB3 is linked to neoplasm.