ERBB2 and neoplasm: A9B5-Bs-5 and A9B5-Bs-7, in which the nanobody A9B5 is fused to the N-terminus of light chain via a (GGGGS)3 flexible linker, retained high binding affinity (EC50 < 2 nM) for both wild-type and chimeric HER2-ECD proteins and achieved high binding saturation on HER2-positive tumor cells (Figures 2D, E).