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Cholecystokinin-2 Receptor Targeting with Novel C-terminally Stabilized HYNIC-Minigastrin Analogs Radiolabeled with

Maximilian Klingler1, Christine Rangger2, Dominik Summer3

  • 1Department of Nuclear Medicine, Medical University of Innsbruck, Anichstrasse 35, A-6020 Innsbruck, Austria. maximilian.klingler@i-med.ac.at.

Pharmaceuticals (Basel, Switzerland)
|January 18, 2019
PubMed

Insights

New technetium-99m (99mTc)-labeled minigastrin analogs show promise for targeting cholecystokinin-2 receptors (CCK2R) in tumors. These radioligands demonstrate high tumor uptake and stability, supporting their potential for cancer diagnosis and therapy.

Area of Science:

  • Nuclear Medicine
  • Radiopharmaceutical Chemistry
  • Oncology

Background:

  • Overexpression of cholecystokinin-2 receptors (CCK2R) in tumors like medullary thyroid carcinoma enables targeted imaging and therapy.
  • Technetium-99m (99mTc)-labeled radiopharmaceuticals offer ideal imaging characteristics, availability, and cost-effectiveness.

Purpose of the Study:

  • To develop and evaluate novel hydrazinonicotinic acid (HYNIC) conjugated minigastrin analogs for CCK2R-targeted imaging.
  • To assess the stability, tumor targeting, and biodistribution of two new 99mTc-labeled peptide conjugates.

Main Methods:

  • Synthesis of two HYNIC-conjugated minigastrin analogs with specific amino acid substitutions.
  • Labeling with 99mTc at high specific activity.
  • In vitro analysis of CCK2R affinity and cell uptake using A431 cells (CCK2R-transfected and mock-transfected).
  • In vivo metabolic stability studies in BALB/c mice.
  • Biodistribution studies in athymic BALB/c nude mice bearing A431-CCK2R xenografts.

Main Results:

  • Both radioligands exhibited high resistance to enzymatic degradation in vivo.
  • Significant tumor uptake was observed: 24.75 ± 4.38% IA/g for [99mTc]Tc-HYNIC-MGS5 and 42.48 ± 6.99% IA/g for [99mTc]Tc-HYNIC-MGS11 at 4 hours post-injection.
  • Tumor-to-kidney ratios were comparable (2.6–3.3), with kidneys showing high excretion (7.8–19.9% IA/g).

Conclusions:

  • The developed 99mTc-labeled minigastrin analogs demonstrate excellent stability and high tumor targeting capabilities for CCK2R-expressing xenografts.
  • These compounds show potential for diagnostic imaging and therapeutic applications in CCK2R-positive cancers.
  • Further evaluation is warranted for their potential use in radioguided surgery.
Keywords:
cholecystokinin-2 receptorhydrazinonicotinic acid (HYNIC)minigastrinmolecular imagingradiometalstechnetium-99m

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