Synthesis and evaluation of copper radiopharmaceuticals with mixed bis(thiosemicarbazone) ligands

Lily J. Ackerman, Douglas X. West, Carla J. Mathias, Mark A. Green

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21 Scopus citations

Abstract

Four 'mixed' bis(thiosemicarbazone) derivatives of pyruvaldehyde were synthesized that incorporate two dissimilar thiosemicarbazone functions. The corresponding [67Cu]copper(II) complexes were prepared and evaluated as possible copper radiopharmaceuticals. The pyruvaldehyde-based mixed bis(thiosemicarbazone) ligands, CH3C[=NNHC(S)NHMe]CH[=NNHC(S)NHEt] (1), CH3C[=NNHC(S)NHMe] CH[=NNHC(S)NEt2] (2), CH3C[=NNHC(S)NHMe]CH[=NNHC(S)- cyclo-N(CH2)5] (3), and CH3C [=NNHC(S)NHMe]CH[=NNHC(S)-cyclo-N(CH2)6] (4), were obtained by reaction of the appropriate thiosemicarbazide derivative with pyruvaldehyde-2-N4-methylthiosemicarbazone (CH3C[=NNHC(S) NHMe]CHO). The 67Cu-labeled copper(II) complexes of ligands 1-4 were prepared and screened in a rat model to assess the potential of each chelate as a 62Cu-radiopharmaceutical for imaging with positron emission tomography. The 67Cu-complexes of ligands 1-4 exhibit significant uptake into the brain and heart 1 min following intravenous administration to rats. For the 67Cu-complexes of ligands 2, 3, and 4, the cerebral and myocardial uptake of 67Cu is two-to-threefold lower at 2 h than at 1 min postinjection, due to significant biological clearance of these 67Cu- chelates. However, the 67Cu-complex of 1 affords cerebral and myocardial uptake and retention comparable to that of [67Cu]Cu-PTSM in this model. Although the kinetics of this new agent appear attractive, ultrafiltration studies using solutions of dog and human serum albumin reveal that the 67Cu-complex of ligand 1, like Cu-PTSM, interacts more strongly with human albumin than dog albumin. Thus, this new agent would appear to offer no advantage over Cu-PTSM as a 62Cu-labeled tracer for evaluation of regional tissue perfusion.

Original languageEnglish (US)
Pages (from-to)551-554
Number of pages4
JournalNuclear Medicine and Biology
Volume26
Issue number5
DOIs
StatePublished - Jul 1999

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Keywords

  • Copper
  • PET
  • Radiopharmaceutical
  • Thiosemicarbazone

ASJC Scopus subject areas

  • Molecular Medicine
  • Radiology Nuclear Medicine and imaging
  • Cancer Research

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