Synthesis of radioiodinated analogs of 2-phenylpyrazolo[4,3-c]-quinolin-3 (5H)-one by a modified triazene method

Synthesis and testing of a triaza-cyclopenta[b]phenanthrene scaffold as a DNA binding agent

A novel DNA binding agent based upon a triaza-cyclopenta[b]phenanthrene scaffold, compound 1, has been synthesized. dsDNA binding analysis of this compound using the ethidium bromide displacement assay indicated a preference for GC-rich sequences. However, equilibrium dialysis experiments against a variety of nucleic acids showed that the target compound bound about 20-fold tighter to G-quartet DNA than to dsDNA under physiological salt concentrations. The binding of 1 to G-quartet DNA was verified by the ability of the compound to promote the formation of the quartet and to compete with TmPyP4 for binding to the quadruplex. Given the importance of G-quartet binding agents in the treatment of cancer and in the understanding of drug-DNA interactions, 1 and its related analogs should find utility as a new class of G-quartet specific agents.

Current and future radiopharmaceuticals for brain imaging with single photon emission computed tomography

Development of radiopharmaceuticals for functional brain imaging has progressed rapidly in recent years. Measurement of regional cerebral blood flow in humans can be achieved by using [123I]-iodoamphetamine or [99mTc]-HMPAO. Several other lipid-soluble [99mTc]-technetium complexes are currently undergoing clinical trials. New 123I-labeled agents designed to measure central nervous system receptors, including D1 and D2 dopamine, serotonin, muscarinic, and benzodiazepine receptors, have been developed. In conjunction with single photon emission computed tomography, they may provide useful tools to evaluate brain function related to changes in receptor concentration.

Where have we got to with neuroreceptor mapping of the human brain?

In the past two decades, tritiated radioligand receptor binding, a tool commonly used to investigate the site of action of drugs in laboratory animals, has provided a vast body of information on neuropharmacology and neurobiology. Several neurological and psychiatric diseases have been related to neurotransmitter and receptor disorders. In order to study ligand interactions with receptors in vivo in humans, new tracers capable of carrying a gamma-emitting radionuclide to the receptor have been designed. Emission computerized tomography (ECT) techniques such as positron (PET) or single photon emission tomography (SPET) allow monitoring of the time-course of regional tissue concentration of these radiolabelled ligands. PET and SPET each have their inherent advantages and drawbacks. The cyclotron-based technology of PET is a demanding and expensive technique that, to date, is still mainly reserved for research purposes. It is hoped that once the scientific basis of a physiopathological study is established using PET, diagnostic information might be provided by the more readily available SPET technology. The purpose of this article is to review the current state of receptor-binding gamma-emitting radioligands and to present the clinical potential of these new kinds of radiopharmaceuticals in clinical investigation.

Synthesis and biodistribution of an 123I labelled flunitrazepam derivative: a potential in vivo tracer for benzodiazepine receptors

A method for the synthesis of no-carrier-added of 7-[123I]iodo-1,3-dihydro-5-(2-fluorophenyl)-1-methyl-2H-1,4- benzodiazepine-2-one with a radiochemical yield of 25-30% has been developed. This benzodiazepine was prepared by reaction of [123I]iodide with the corresponding piperidyltriazene in acid medium and the reaction has been optimized for solvent, time and temperature. The triazene was synthesized by reduction of flunitrazepam to the amine, diazotisation and coupling with piperidine. Biodistribution studies of this radioligand in rats showed a maximum brain uptake of 0.35% of the injected dose at 15 min, which decline to 0.02% at 120 min.