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Stabilized Sarabesin-3 for prostate imaging
Results Radiolabeling
The RCP and radiometal incorporation were both >90%.
Internalization studies
In internalization experiments with [111In]SB3 in PC-3 cells, the membrane faction contained almost 4 times more radioactivity compared to the cell faction.
Competition binding assay
Quantified binding of [125I]Tyr4-bombesin to PC259 tissue sections without and with increasing concentrations of unlabeled SB3 resulted in an IC50 value of 3.5 nM (95% CI: 1.9 nM to 6.4 nM) (Fig. 3).
Figure 3 Competitive binding assay using [125I]Tyr4-bombesin blocked with increasing concentrations of unlabeled SB3. 95% CI is shown in green.
Stability studies
In vivo stability of [111In]SB3 -/+ PA was analyzed in blood samples, collected 5 min p.i. In the animals receiving 200 pmol [111In]SB3 37.3±2.5 % of the remaining circulating activity consisted of intact radiotracer, while this value significantly increased (P<0.0001) to 86.7±1.5 % when [111In]SB3 was co-injected with PA (Fig. 4 A+B). When a 10× higher peptide amount was administered, these values were 42.0±0.2 % vs 87.9±1.1 % (P<0.0001) of the radiotracer still being
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