Abstract
Radioiodinated pharmaceuticals are convenient tracers for clinical and research investigations because of the relatively long half‐lives of radioactive iodine isotopes (i.e., 123I, 124I, and 131I) and the ease of their chemical insertion. Their application in radionuclide imaging and therapy may, however, be hampered by poor in vivo stability of the C–I bond. After an overview of the use of iodine in biology and nuclear medicine, we present here a survey of the catabolic pathways for iodinated xenobiotics, including their biodistribution, accumulation, and biostability. We summarize successful rational improvements in the biostability and conclude with general guidelines for the design of stable radioiodinated pharmaceuticals. It appears to be necessary to consider the whole molecule, rather than the radioiodinated fragment alone. Iodine radionuclides are generally retained in vivo on sp2 carbon atoms in iodoarenes and iodovinyl moieties, but not in iodinated heterocycles or on sp3 carbon atoms. Iodoarene substituents also have an influence, with increased in vivo deiodination in the cases of iodophenols and iodoanilines, whereas methoxylation and difluorination improve biostability.
Highlights
Zhang and co-workers recently studied the metabolism of ortho-iodoanilines and discovered that, after an initial oxidation, ortho-iodoanilines of type are conjugated with a GSH molecule, resulting in the 2-deiodinated adducts (Scheme 13).[51]
The deiodination rate of each pharmaceutical analyzed has been correlated with the specific structural features of the iodination site and of the whole molecule, modeling the biological pathways that those radioiodinated pharmaceuticals were likely to undergo to lead to deiodination
The results reviewed indicate that proteolysis plays a major role – even more important than that played by deiodinases – in the deiodinating catabolism of radioiodinated peptides and proteins
Summary
The diet is deficient in iodine.[3]. In the stomach iodide is believed to have a role in regulating the gastric pH.[4]. Klaren (top right, born May 30, 1961) studied biology at Radboud University, where he graduated in 1989 and obtained his Ph.D. in animal physiology in 1995 He worked as a postdoctoral research associate at the University of Sheffield, UK (1995–1998), on intestinal ion transport in cystic fibrosis, and in 1998 was appointed research lecturer at the Faculty of Veterinary Medicine of Utrecht University, where he investigated the uptake and metabolism of thyroid hormone in cardiac and skeletal muscle cells. Awards include the Gold Medal of the Royal Netherlands Chemical Society (KNCV, 2002), the AstraZeneca award for research in organic chemistry (2003), and Most Entrepreneurial Scientist of the Netherlands (2008) He is co-founder of the spin-off companies Chiralix and FutureChemistry, and currently President of the KNCV and Vice-Dean of Education at the Faculty of Science, Radboud University. If the tracer is deiodinated in the brain, the iodide might be expelled too slowly, resulting in a low signal-to-noise ratio in the area of interest
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