CCKBR and neoplasm: In order to evaluate the influence of the different SiFA moieties paired with a reduced number of negative charges within the linker sequence of rhCCK derivatives on in vivo performance, particularly with regard to kidney retention, we decided to further investigate both [177Lu]Lu-DOTA-rhCCK-70 (apparent IC50 = 12.6 ± 2.0 nM, logD7.4 = − 1.67 ± 0.08) and [177Lu]Lu-DOTA-rhCCK-91 (apparent IC50 = 8.7 ± 0.7 nM, logD7.4 = − 1.66 ± 0.08) at 24 h p.i. in AR42J tumor-bearing mice, since both displayed acceptable CCK-2R affinity and lipophilicity.