CD33 and neoplasm: The ex vivo biodistribution study confirmed the significant higher tumor targeting for anti-CD33 Nbs (tumor uptake from 1.91 ± 0.64%IA/g to 2.53 ± 0.69%IA/g), compared to Nb_16 (tumor uptake of 0.70 ± 0.13%IA/g) and to the non-targeting control 99mTc-ctrl_Nb (tumor uptake of 0.16 ± 0.04%IA/g) (Figure 7A,B and Table 3).