As alternative antibodies formats such as Fab fragments could have potential advantages for delivering radionuclides to the tumors due to their easier tumor penetration and fast clearance from the circulation, in this study we generated Fab fragments of the same anti-CCR8 antibody used in [7] and evaluated their pharmacokinetics side by side with the whole anti-CCR8 IgG in CT26 and MC38 murine colorectal cancer models. The gene discussed is CCR8; the disease is neoplasm.