Table 2. Summary of SST2 Binding Data for a Series of 64Cu-Labeled TATE Derivatives Using MPC Cell Homogenates and Intact MPC Cells.
| MPC cell homogenate |
intact MPC cells |
|||||
|---|---|---|---|---|---|---|
| 64Cu-labeled compounda | Kd (nM)b | Bmax (fmol/mg of protein)b | Kd (nM)b | Bmax (fmol/mg of protein)b | uptake fraction (%)c | Kd ratioe |
| DOTA-TATE | 2.03 (0.48) | 562 (218) | 1.19 (0.16) | 471 (31) | 56 | 1.70 |
| TATE | 3.05 (0.16) | 965 (582) | 1.43 (0.39) | 420 (77) | 64d | 2.13 |
| Pra-PEG2-TATE | 4.48 (0.57) | 488 (144) | 3.33 (0.83) | 229 (89) | 48 | 1.35 |
| cLAB1-TATE | 6.31 (0.99) | 1191 (334) | 1.73 (0.35) | 339 (73) | 66 | 3.66 |
| cLAB4-TATE | 3.67 (3.30–4.09)d | 396 (384–408)d | 2.77 (0.62) | 600 (50) | 64 | 1.32 |
| NES1-TATE | 6.94 (6.19–7.78) | 220 (212–229) | 3.01 (0.65) | 478 (175) | 49d | 2.31 |
| NES2-TATE | 18.2 (14.2–23.7) | 288 (257–327) | 2.94 (0.85) | 401 (145) | 56d | 6.19 |
| NES3-TATE | 5.01 (4.04–6.20) | 275 (257–294) | 2.76 (2.33–3.25)d | 371 (354–389)d | 68d | 1.82 |
| NES4-TATE | 5.64 (3.66–8.71) | 606 (532–698) | 2.65 (1.93–3.64)d | 586 (532–649)d | 53d | 2.13 |
| NES5-TATE | 12.0 (1.50) | 731 (189) | 2.40 (1.34) | 393 (190) | 62d | 5.01 |
| JR11 | 5.35 (5.06–5.65) | 764 (751–778) | 8.17 (7.38–9.04) | 717 (691–744) | 28 | 0.65 |
After 64Cu-labeling, the non-labeled ligand was not separated or saturated with natCu2+.
Data shown are mean values with calculated confidence interval of 68% of one experiment, which was performed in duplicate or triplicate, or mean values ±SEM of 2–3 or 6 (in case of [64Cu]Cu-NODAGA-TATE toward intact MPC cells) experiments, which were also performed in duplicate or triplicate.
The uptake fraction (“internalized” or not acid releasable radioligand) is expressed as percentage of specific total-bound radioligand (Figure S4 in the Supporting Information).
Data were previously published by us (adapted with permission from Brandt et al.16 Copyright 2022 American Chemical Society and Brandt et al.17 Copyright 2023, American Chemical Society).
Ratio of Kd (cell homogenate)/Kd (intact cells). If not otherwise stated, the compounds bear NODAGA as chelator moiety for complexation of copper-64.