Tetraamine-modified octreotide and octreotate: labeling with 99mTc and preclinical comparison in AR4-2J cells and AR4-2J tumor-bearing mice.

Two somatostatin analogues, [(99m)Tc]Demotide and [(99m)Tc]Demotate 4, were compared with [(99m)Tc]Demotate 1, a previously reported somatostatin receptor subtype 2 (sst(2)) targeting tracer. Conjugates were prepared by coupling an open-chain tetraamine chelator to D-Phe(1) of [Tyr(3)]-octreotide or [Tyr(3)]-octreotate, respectively, via a p-benzylaminodiglycolic acid spacer adopting solid-phase peptide synthesis techniques. Peptide conjugates were collected in a highly pure form after chromatographic purification.

[99mTc]Demotate, a new 99mTc-based [Tyr3]octreotate analogue for the detection of somatostatin receptor-positive tumours: synthesis and preclinical results.

Demotate is a new tetraamine-functionalised [Tyr3]octreotate derivative that binds technetium-99m with a high efficiency under mild conditions. The resulting radioligand, [99mTc]Demotate, forms in a high purity and is stable for at least 6 h after labelling. The affinity of the unlabelled peptide for somatostatin receptors is high (IC(50)=0.