Chemical and biological properties of 2,6-diisopropyl IDA labelled with 99mTc

[Technetium-99m radiopharmaceuticals for in vivo diagnostics]

INTRODUCTION

Technetium-99m is an ideal radionuclide with optimum decay characteristics. It can be obtained in sterile, pyrogen-free and carrier-free condition, as sodium pertechnetate (Na99mTcO4), from 99Mo/99mTc generator. Because of its six-hour physical half-life and monochromatic 140 keV photons free of -radiation, administration of small amounts of 99mTc solution is possible, without a significant radiation damage to the patient. Technetium eluted from the 99Mo/99mTc generator is in the highest oxidation form (+ 7). It can be used for diagnostic purposes alone, but it is often used for labeling different organic and inorganic compounds. As it is unreactive, reduction with a chemical reductant, (+1), (+3) and (+5) oxidation are necessary before use. Nowadays almost 80% of radiopharmaceuticals are based on 99mTc.

RADIOPHARMACEUTICALS

Radiopharmaceuticals are radionuclides or radioactive compounds used in diagnosis and therapy of human diseases. A pharmaceutical is chosen based on its localization in the organ, or its participation in its physiological function. Radiation emitted from a radionuclide is detected by a radiation detector. The ability to incorporate available radionuclides into tracer molecules has been the main goal in developing radiopharmaceuticals. As radionuclides with nuclear characteristcs used as either diagnostic or therapeutic radiopharmaceuticals, are predominantly metals, they can be designed as metal essential, whereby biological distribution is determined by coordination compound, or metal tagged, in which case the properties of the carrier molecule (ligand system) determine the biological distribution. This paper reviews the development of 99mTc-radiopharmaceuticals.

A Potential Dubin-Johnson Syndrome Imaging Agent: Synthesis, Biodistribution, and MicroPET Imaging

Dubin-Johnson syndrome (DJS) is caused by a deficiency of the human canalicular multispecific organic anion transporter (cMOAT). A new lipophilic copper-64 complex of 1,4,7-tris(carboxymethyl)-10-(tetradecyl)-1,4,7,10-tetraazadodecane (5) was prepared and evaluated for potential as a diagnostic tool for DJS. The prepared ligand was labeled with (64)Cu citrate in high radiochemical purity. In vivo uptake and clearance of the complex was determined through biodistribution studies using normal Sprague-Dawley rats and mutant cMOAT-deficient (TR(-)) rats. In normal rats, the radioactive copper complex was cleared quickly from the body exclusively through the hepatic pathway. The (64)Cu complex was taken up rapidly by the liver and quickly excreted into the small intestine and then the upper large intestine, whereas <1% ID/organ was found in the kidney at all time points post injection. Whereas activity was accumulated continuously in the liver of TR(-) rats, it was not excreted into the small intestine. MicroPET studies of normal and TR(-) rats were consistent with biodistribution data and showed dramatically different images. This study strongly suggests that cMOAT is involved in excretion of (64)Cu-5. The significant difference between the biodistribution data and microPET images of the normal and TR(-) rats demonstrates that this new (64)Cu complex may allow noninvasive diagnosis of DJS in humans.