Related Experiment Video
Updated: Feb 13, 2026

Ex Vivo Release of Calcitonin Gene-Related Peptide from the Trigeminovascular System in Rodents
Published on: May 16, 2022
New Gastrin Releasing Peptide Receptor-Directed [99mTc]Demobesin 1 Mimics: Synthesis and Comparative Evaluation
Berthold A Nock1, David Charalambidis1, Werner Sallegger2
1Molecular Radiopharmacy, INRASTES , National Center for Scientific Research "Demokritos" , GR-153 10 Athens , Greece.
Abstract:
We have previously reported on the gastrin releasing peptide receptor (GRPR) antagonist [99mTc]1, ([99mTc]demobesin 1, 99mTc-[N4'-diglycolate-dPhe6,Leu-NHEt13]BBN(6-13)). [99mTc]1 has shown superior biological profile compared to analogous agonist-based 99mTc-radioligands. We herein present a small library of [99mTc]1 mimics generated after structural modifications in (a) the linker ([99mTc]2, [99mTc]3, [99mTc]4), (b) the peptide chain ([99mTc]5, [99mTc]6), and (c) the C-terminus ([99mTc]7 or [99mTc]8). The effects of above modifications on the biological properties of analogs were studied in PC-3 cells and tumor-bearing SCID mice. All analogs showed subnanomolar affinity for the human GRPR, while most receptor-affine 4 and 8 behaved as potent GRPR antagonists in a functional internalization assay. In mice bearing PC-3 tumors, [99mTc]1-[99mTc]6 exhibited GRPR-specific tumor uptake, rapidly clearing from normal tissues. [99mTc]4 displayed the highest tumor uptake (28.8 ± 4.1%ID/g at 1 h pi), which remained high even after 24 h pi (16.3 ± 1.8%ID/g), well surpassing that of [99mTc]1 (5.4 ± 0.7%ID/g at 24 h pi).
Related Concept Videos
Preparation of 1° Amines: Azide Synthesis
Azide ions act as good nucleophiles and react with unhindered alkyl halides to form alkyl azides. Alkyl azides do not participate in further nucleophilic substitution reactions, thereby eliminating the chances of polyalkylated products. Alkyl azides are reduced by hydride-based reducing agents, like lithium aluminum...
Preparation of 1° Amines: Gabriel Synthesis
Strong bases like NaOH or KOH deprotonate the phthalimide to form the corresponding anion, which acts as a nucleophile. Further, the anion attacks an...
Peptide Bonds
Evaluating Limits by Direct Substitution
Internal Receptors
Comparative Excretory Systems

