Evaluation of [ 125I]7α-O-iodoallyl diprenophine as a new potential spect opioid receptor imaging agent

A new iodinated diprenorphine analog, [ 125I]7α-O-iodoallyl diprenorphine ([ 125I]7α-O-IA-DPN), was prepared by iododestannylation and characterized. As an opioid antagonist, this agent showed very high affinity (K i = 0.4 ± 0.2 nM) and 63% of specific binding by in vitro and in vivo binding studies. Inhibition curves indicated that this tracer labeled with the same affinities to three opioid receptors (μ = δ = κ). The findings demonstrate that this proposed compound appears to be a potential radioprobe for future study of opioid receptors by in vivo SPECT.