ALB and neoplasm: Similar to previously published rhCCK derivatives [19], tumor and kidney uptake for [177Lu]Lu-DOTA-rhCCK-18 was high at 1 h p.i. and remained high at 24 h p.i. Elevated tumor and stomach retention can be attributed to the decelerated clearance kinetics (higher logD7.4 and albumin binding) of the rhCCK ligands and their prolonged bioavailability, the increased kidney retention is likely caused by a synergistic effect of the negatively charged side chains in proximity of the SiFA building block.