Serotonin 2A Receptor (5-HT_2AR) Activation by 25H-NBOMe Positional Isomers: In Vitro Functional Evaluation and Molecular Docking

Abstract

Serotonergic psychedelics are defined as compounds having serotonin 2A receptor (5-HT2AR) activation as an important pharmacological mechanism. These compounds include the phenylalkylamine class, containing substances with e.g. 2C-X structures (phenethylamines) or their N-methoxybenzyl analogues (NBOMes). Besides their abuse potential, psychedelics are increasingly recognized for having therapeutic benefits. However, many psychedelics remain incompletely characterized, even concerning their structure–activity relationships. Here, five positional isomers of 25H-NBOMe, with two methoxy groups on the different positions of the phenyl ring of the phenethylamine moiety, were subjected to split-nanoluciferase assays assessing the in vitro recruitment of cytosolic proteins to the 5-HT2AR. Furthermore, molecular docking at the 5-HT2AR allowed estimation of which residues interact with the specific isomers’ methoxy groups. Although the optimal substitution pattern of N-unsubstituted phenylalkylamines has been extensively studied, this is the first comparative evaluation of the functional effects of the positioning of the methoxy groups in the phenethylamine moiety of NBOMes.

Behavioral and neurochemical effects of novel N-Benzyl-2-phenylethylamine derivatives in adult zebrafish

“…These findings also fit well with recent pilot in vitro data demonstrating higher 5HT2A receptor activation by 2,4-than 3,4-dimethoxylated NBOMe and NBF derivatives 63,64 .…”

“…In contrast, most of 3,4-dimethoxy derivatives were behaviorally and neurochemically inert, except for 34H-NBOMe(F), that was highly anxiolytic and hallucinogenic, albeit at concentrations significantly higher than its 2,4-dimethoxy isomer, 24H-NBOMe(F). These findings also fit well with recent pilot in vitro data demonstrating higher 5HT 2A receptor activation by 2,4- than 3,4-dimethoxylated NBOMe and NBF derivatives 63, 64 .…”

“…Several positional isomers of 25H-NBOMe that differ in the mutual arrangement of two methoxy groups in the phenylethylamine moiety exhibit high affinity for this receptor (assessed in vitro for binding at human 5-HT 2A ) 63 . At the same time, their higher potency (EC50) is due to the obligatory presence of one of the two methoxy groups at position 2 of the phenylethylamine moiety, and the presence of a methoxy group at position 3 significantly reduces potency (EC50) to activate this receptor in vitro.…”

Molecular and Functional Imaging Studies of Psychedelic Drug Action in Animals and Humans

“…Early research into structure-function indicated that methylation of ergotamines at the N 1 position enhances serotonin antagonism in the isolated rat uterus assay [ 66 ], while decreasing hallucinogenic potency predicted from a quantitative structure-activity relationship (QSAR) study [ 67 ]. N -methyl-2-[ 125 I]-iodo-lysergic acid diethylamide ([ 125 I]-MIL, 24 ) was developed as a presumably non-hallucinogenic ligand for the molecular imaging of serotonin receptors, whereby N - methylation of [ 125 I]-LSD ( 25 ) was intended to impart greater selectivity and sensitivity for 5HT 2 receptors [ 23 ].…”

“…Binding assays against [ 3 H]-ketanserin/[ 3 H]-mesulergine, [ 3 H]-LSD and [ 3 H]-Cimbi-36 in vitro showed that 25CN-NBOH ( 13 , N -(2-hydroxybenzyl)-2,5-dimethoxy-4-cyanophenylethylamine) had >52-fold K i 2C / K i 2A selectivity ratio and a 37-fold K i 2B / K i 2A ratio, and likewise showed substantial 5HT 2A selectivity in functional assays of IP turnover. Various isomers of 25H-NBOMe in which the two methoxy-groups are in different positions (ortho, meta, and para) were compared with respect to their efficacy in activating signaling pathways, in conjunction with molecular docking studies at the 5HT 2A receptor binding pocket [ 66 ]. In the series examined, several dimethoxy compounds proved to have an efficacy exceeding that of LSD ( 1 ).…”