123I-MSP and F[11C]MSP: New selective 5-HT2A receptor radiopharmaceuticals for in vivo studies of neuronal 5-HT2 serotonin receptors. Synthesis, in vitro binding study with unlabelled analogues and preliminary in vivo evaluation in mice

5‐HT radioligands for human brain imaging with PET and SPECT

“…After the butyrophenones emerged as the foundation for 5‐HT 2A selective antagonist ligands, F[ 11 C]MSP (8‐[3‐(4‐fluorobenzoyl)propyl]‐1‐methyl‐1,3,8‐triazaspiro[4,5]decan‐4‐one) and [ 123 I]MSP (8‐[3‐(4‐iodobenzoyl)propyl]‐1‐methyl‐1,3,8‐triazaspiro[4,5]decan‐4‐one) were developed as potential PET and SPECT ligands, respectively . F[ 11 C]MSP was quickly abandoned, due to problems with low specific radioactivity.…”

Radiotracers for the Central Serotoninergic System

“…[ 123 I]MSP was designed to maintain the affinity for 5-HT 2A R of spiperone while decreasing its affinity toward dopaminergic D2 and D3 receptors. The study carried out with [ 123 I]MSP evidenced a strong affinity and selectivity for 5-HT 2A R, with a radiolabeling distribution in correlation with those obtained with the reference radiotracers (intense labeling of the mouse frontal cortex) [ 159 ]. Despite promising results, [ 123 I]MSP has not been the subject of recent studies.…”

New Trends and Current Status of Positron-Emission Tomography and Single-Photon-Emission Computerized Tomography Radioligands for Neuronal Serotonin Receptors and Serotonin Transporter

“…8-[3-(4-Iodobenzoyl)­propyl]–1-methyl-1,3,8-triazaspiro­[4,5]­decan-4-one ([ 123 I]­MSP) is the spiperone-derived analogue that showed better selectivity toward 5HT2A over other receptors. In mice, the pharmacokinetic and binding studies indicated that the regional distribution of the radioligand was corresponding to that of 5HT2A-receptor-rich regions and also exhibited significant brain uptake with good retention capability . [ 123 I]­MSP displayed promising selectivity and specificity toward 5HT2A receptors, as validated by the attenuation in its uptake following treatment of mice with IMSP and ritanserin .…”

“…In mice, the pharmacokinetic and binding studies indicated that the regional distribution of the radioligand was corresponding to that of 5HT2A-receptor-rich regions and also exhibited significant brain uptake with good retention capability. 140 [ 123 I]MSP displayed promising selectivity and specificity toward 5HT2A receptors, as validated by the attenuation in its uptake following treatment of mice with IMSP and ritanserin. 140 Although the preliminary studies have shown that [ 123 I]MSP could be a promising candidate for SPECT imaging of 5HT2A receptors, detailed investigations are still warranted.…”