Novel 99m Tc(III) Complexes [ 99m TcCl(CDO)(CDOH) 2 B-R] (CDOH 2 = Cyclohexanedione Dioxime) Useful as Radiotracers for Heart Imaging

Bioconjug Chem. 2016 Nov 16;27(11):2770-2779. doi: 10.1021/acs.bioconjchem.6b00552. Epub 2016 Oct 24.

Abstract

In this study, we evaluated seven new 99mTc(III) complexes [99mTcCl(CDO)(CDOH)2B-R] (99mTc-2Fboroxime: R = 2-formylfuran-3-yl (2F); 99mTc-3Fboroxime: R = furan-3-yl (3F); 99mTc-5Fboroxime: R = 5-formyfuran-2-yl (5F); 99mTc-HPboroxime: R = 6-hydroxylpyridin-2-yl (HP); 99mTc-MPYboroxime: R = 5-methoxypyridin-3-yl (MPY); 99mTc-PMboroxime: R = 1,5-pyrimidin-3-yl (PM); and 99mTc-4PYboroxime: R = pyridin-4-yl (4PY)) for their potential as heart imaging agents. All new 99mTc(III) radiotracers except 99mTc-2Fboroxime were prepared with high radiochemical purity (RCP > 95%). The low RCP (∼75%) for 99mTc-2Fboroxime is most likely caused by steric hindrance from the 3-formyl group. Biodistribution and imaging studies were performed in SD rats. Planar image quantification was performed to compare their myocardial retention times. We found that the myocardial washout curves of new 99mTc(III) radiotracers were best fitted the biexponential decay function. The AUC (area under the curve) values followed the general trend: 99mTc-5Fboroxime (129 ± 6) > 99mTc-3Fboroxime (114 ± 11) > 99mTc-Teboroxime (104 ± 16) > 99mTc-MPYboroxime (92 ± 18) > 99mTc-4PYboroxime (77 ± 10) > 99mTc-PMboroxime (68 ± 14) ≈ 99mTc-HPboroxime (62 ± 14). The 2 min heart uptake values from biodistribution studies follow the ranking order of 99mTc-5Fboroxime (3.75 ± 0.15%ID/g) ≈ 99mTc-MPYboroxime (3.73 ± 0.24%ID/g) > 99mTc-PMboroxime (3.47 ± 0.15%ID/g) ≈ 99mTc-3Fboroxime ≈ (3.25 ± 0.77%ID/g). The 5 min heart uptake of 99mTc-5Fboroxime (3.91 ± 0.09%ID/g) was almost identical to its 2 min heart uptake (3.75 ± 0.15%ID/g), and its 15 min heart uptake value (2.83 ± 0.08%ID/g) compared well to the 2 min heart uptake of 99mTc-Teboroxime (3.00 ± 0.37%ID/g). It took ∼5 min for 99mTc-5Fboroxime to approach the 1 min heart uptake value of 99mTc-Teboroxime (∼3.5% ID/g) and ∼9.5 min to reach the 2 min heart uptake value of 99mTc-Teboroxime (∼3.0% ID/g). The best image acquisition window is 0-5 min for 99mTc-5Fboroxime. High-quality single-photon emission computed tomography images of the rat hearts were acquired in any of the 5 min window over the first 20 min after its administration. 99mTc-5Fboroxime has significant advantages over 99mTc-Teboroxime as the radiotracer for myocardial perfusion imaging.

MeSH terms

  • Animals
  • Heart / diagnostic imaging*
  • Kinetics
  • Myocardial Perfusion Imaging
  • Organotechnetium Compounds / chemical synthesis
  • Organotechnetium Compounds / chemistry*
  • Organotechnetium Compounds / pharmacokinetics
  • Oximes / chemistry
  • Radioactive Tracers
  • Radiochemistry
  • Rats
  • Rats, Sprague-Dawley
  • Tissue Distribution
  • Tomography, Emission-Computed, Single-Photon / methods*

Substances

  • Organotechnetium Compounds
  • Oximes
  • Radioactive Tracers