6-[123I]Iodo-2-[[4-(2-methoxyphenyl)piperazin-1-yl]methyl]imidazo[1,2-a]pyridine as potential SPECT agent for imaging dopamine D4 receptor:: synthesis and in vivo evaluation in a nonhuman primate

The dopamine D-4 receptor subtype has drawn considerable attention due to its potential implication in schizophrenia and erectile dysfunction. 6-[I-123]Iodo-2-[[4-(2-methoxyphenyl)piperazin-1-yl]methyl]imidazo[1,2-a]pyridine [I-123]-1, a potent and selective new dopamine D-4 agonist, was synthesized by classical iododestannylation using sodium [I-123]iodide and chloramine-T. Radiolabeling yield varied from 34 to 38% with a radiochemical purity exceeding 99%. Despite a good in vitro profile, in vivo evaluation of this radioligand in baboon showed no brain uptake after i.v. injection.