25CN‐NBOH: A Selective Agonist for in vitro and in vivo Investigations of the Serotonin 2A Receptor

Abstract

4-(2-((2-hydroxybenzyl)amino)ethyl)-2,5-dimethoxybenzonitrile (25CN-NBOH) was first reported as a potent and selective serotonin 2A receptor (5-HT 2A R) agonist in 2014, and it has since found extensive use as a pharmacological tool in a variety of in vitro, ex vivo and in vivo studies. 25CN-NBOH is readily available from a synthetic perspective using standard chemical transformations, and displays favorable physiochemical properties in terms of stability and solubility. Due to its superior selectivity for 5-HT 2A R, 25CN-NBOH has been used to investigate the effects of selective 5-HT 2A R activation in vivo, and has thus become an important pharmacological tool for the exploration of 5-HT 2A R signaling in a range of animal models. In the present review, we outline the discovery of 25CN-NBOH, its pharmacological profile and major findings from studies where it has been used.

Discovery of β-Arrestin-Biased 25CN-NBOH-Derived 5-HT2AReceptor Agonists

“… 29 − 31 The most notable exceptions are 25CN-NBOH 32 − 35 and ( S,S )-DMBMPP, 36 which are the most selective 5-HT 2A R agonists reported to date, with a 52- to 100-fold and 124-fold selectivity over 5-HT 2C R, respectively. 33 , 36 …”

“…Despite these nonselective receptor profiles, the activation of 5-HT 2A R is considered essential for the psychedelic effects as well as the apparent therapeutic potential of these compounds. In general, the phenylalkylamines, and in particular N -benzylphenethylamines (NBOMe’s), have shown selectivity toward 5-HT 2A R. The reader is referred to recent review articles for a more in-depth discussion on the historical overview of the NBOMe class. , Despite efforts from many, the success rate of developing truly selective 5-HT 2A R agonists has been nominal. − The most notable exceptions are 25CN-NBOH − and ( S,S )-DMBMPP, which are the most selective 5-HT 2A R agonists reported to date, with a 52- to 100-fold and 124-fold selectivity over 5-HT 2C R, respectively. , …”

“…29−31 The most notable exceptions are 25CN-NBOH 32−35 and (S,S)-DMBMPP, 36 which are the most selective 5-HT 2A R agonists reported to date, with a 52-to 100-fold and 124-fold selectivity over 5-HT 2C R, respectively. 33,36 The 5-HT 2A R is able to signal through members of both Gα q and Gα i/o protein families and also through beta-arrestin mediated pathways. 37,38 Several psychedelics and 5-HT 2A R agonists have been evaluated for their respective bias profiles toward the Gα q and βarr2 transducers, by means of highly analogous functional complementation assays.…”

Introducing Conformational Restraints on 25CN-NBOH: A Selective 5-HT2A Receptor Agonist

“…In some cases N-benzylation also leads to increased selectivity for 5-HT 2A R over 5-HT 2C R, the epitome of this structure−activity trend being the highly 5-HT 2A Rselective agonist 4-[2-[[(2-hydroxyphenyl)methyl]amino]ethyl]-2,5-dimethoxybenzonitrile (25CN-NBOH, 1, Scheme 1). 8,14 In order to probe the optimal spacial orientation of the highly flexible benzylethylamine chain of the NBOMe scaffold, Nichols in 2013 reported conformationally restricted NBOMe analogs and found 2-(2,5-dimethoxy-4-bromobenzyl)-6-(2methoxyphenyl)piperidine (DMPMBB, 2, Scheme 1) to be ∼100-fold more selective for 5-HT 2A R over 5-HT 2C R in a binding assay. 11 Moreover, 2 displayed an EC 50 value of 74 nM and an R max value of 73% at 5-HT 2A R in a phosphoinositol hydrolysis assay, 11 whereas no functional data for 2 at 5-HT 2C R has been reported to date.…”

“…In some cases N -benzylation also leads to increased selectivity for 5-HT 2A R over 5-HT 2C R, the epitome of this structure–activity trend being the highly 5-HT 2A R-selective agonist 4-[2-[[(2-hydroxyphenyl)­methyl]­amino]­ethyl]-2,5-dimethoxybenzonitrile (25CN-NBOH, 1 , Scheme ). , …”