Pharmacokinetics and dosimetry of iodine-123 labelled PE2I in humans, a radioligand for dopamine transporter imaging

The iodine-123 labelled selective ligand N-(3-iodoprop-2E-enyl)-2-β-carbomethoxy-3β-(4-methylphenyl)nortropane ([¹²³I]PE2I) was evaluated as a probe for in vivo dopamine transporter imaging in the human brain, Six healthy subjects were imaged with a high-resolution single-photon emission tomography scanner. Striatal radioactivity peaked at 1 h after injection. The background radioactivity was low. The volume of distribution in the striatum was 94 ± 24 ml/ml. The results were compared with those of [¹²³I]β-CIT imaging. There was no significant uptake of [¹²³I]PE2I in serotonin-rich regions such as the midbrain, hypothalamus and anterior gingulus, suggesting that in vivo binding is specific for the dopamine transporter. One main polar metabolite of [¹²³I]PE2I was found in plasma, and the parent plasma concentration decayed rapidly. Radiation exposure to the study subject is 0.022 ± 0.004 mSv/MBq (effective dose). The preliminary results suggest that [¹²³I]PE2I is a selective SPET ligand for imaging striatal dopamine transporter density.