PMID: 8683294Jun 1, 1996

Preclinical evaluation of technetium-99m-labeled somatostatin receptor-binding peptides

Journal of Nuclear Medicine : Official Publication, Society of Nuclear Medicine
S VallabhajosulaR T Dean

Abstract

We report here the results of studies on the in vitro receptor binding affinity, in vivo tumor uptake and biodistribution of two 99m-Tc-labeled peptides. Peptides P587 and P829 were synthesized by N-alpha-Fmoc peptide chemistry, purified by reversed-phase HPLC and characterized by fast-atom bombardment mass spectrometry. The peptides were labeled with 99mTc by ligand exchange from 99mTc-glucoheptonate. In vitro somatostatin receptors (SSTR)-binding affinities of P587, P829 and their oxorhenium complexes, [DTPA]octreotide and In-[DTPA]octreotide were determined in an inhibition assay using AR42J rat pancreatic tumor cell membranes and 125I-[Tyr3]somatostatin-14 as the probe. In vivo single- and dual-tracer studies of 99mTc peptides and 111In-[DTPA]octreotide were carried out using Lewis rats bearing CA20948 rat pancreatic tumor implants. Technetium-99m-P587 and 99mTc-P829 of high-specific activity (>60 Ci (2.2 TBq)/mmole) were prepared in >90% radiochemical yield. P587 and P829 had a Ki = 2.5 nM and 10 nM, respectively. [ReO]P587 and [ReO]P829, representing the 99mTc complexes, had Ki = 0.15 nM and 0.32 nM, respectively. In comparison, [DTPA]octreotide and In-[DTPA]octreotide had Ki = 1.6 and 1.2 nM, respectively. In vivo tumor ...Continue Reading

Related Concepts

Neoplasm Transplantation
Neoplasms, Experimental
Malignant Neoplasm of Pancreas
Polypeptides
Rats, Inbred Lew
Technetium 99m
Drug or Chemical Tissue Distribution
Tumor Cells, Cultured
Somatostatin Receptor

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