Gastrin and cholecystokinin peptide-based radiopharmaceuticals: An in vivo and in vitro comparison

Anna Lucia Tornesello, Michela Aurilio, Antonella Accardo, Laura Tarallo, Antonio Barbieri, Claudio Arra, Diego Tesauro, Giancarlo Morelli, Luigi Aloj

Research output: Contribution to journalArticle

Abstract

The development of suitable radioligands for targeting CCK-2 receptor expressing tumors, such as medullary thyroid carcinoma, is of great clinical interest. In the search for the best CCK-2R binding peptides, we have synthesized, evaluated and compared the CCK8 peptide (Asp-Tyr-Met-Gly-Trp-Met-Asp-Phe-NH2) and two gastrin analogs commonly referred to as MG0 (DGlu-Glu(5)-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH2) and MG11 (DGlu(1)-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH2). The N-terminal portion of the three peptide sequences was derivatized by introducing the DTPAGlu or DOTA chelators to allow radiolobeling with 111In(III) and 68Ga(III), respectively. Saturation binding and cellular internalization experiments were performed on A431 cells overexpressing CCK2R (A431-CCK2R). All compounds showed Kd values in the nM range and were internalized with similar rates in CCK2 receptor overexpressing cells. Biodistribution experiments showed higher specific uptake of both MG0-based compounds compared to conjugates containing the CCK8 and MG11 peptide sequences. The higher retention levels of MG0-based peptides were associated with markedly elevated and undesired kidney uptake compared to the other compounds. Current indications suggest that the 5 Glu N-terminal residues while improving peptide stability and receptor-mediated tumor uptake cause unacceptably high kidney retention. Although displaying lower absolute tumor uptake values, the DOTA-coupled CCK8 peptide provided the best tumor to kidney uptake ratio and appears more suitable as lead compound for improvement of radiopharmaceutical properties.

Original languageEnglish
Pages (from-to)405-412
Number of pages8
JournalJournal of Peptide Science
Volume17
Issue number5
DOIs
Publication statusPublished - May 2011

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Keywords

  • Ga and In complexes
  • Minigastrin and CCK8 peptide conjugates
  • Nuclear medicine

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Medicine
  • Molecular Biology
  • Biochemistry
  • Pharmacology
  • Drug Discovery
  • Organic Chemistry

Cite this

Tornesello, A. L., Aurilio, M., Accardo, A., Tarallo, L., Barbieri, A., Arra, C., Tesauro, D., Morelli, G., & Aloj, L. (2011). Gastrin and cholecystokinin peptide-based radiopharmaceuticals: An in vivo and in vitro comparison. Journal of Peptide Science, 17(5), 405-412. https://doi.org/10.1002/psc.1327