The Chemistry and Pharmacology of Synthetic Cannabinoid Receptor Agonist New Psychoactive Substances: Evolution

Metabolic characteristic profiling of 1-amino-3,3-dimethyl-1-oxobutan-2-yl-derived indole and indazole synthetic cannabinoids in vitro

Characterizing the metabolic profiles of synthetic cannabinoids (SCs), a type of new psychoactive substances, is of particular importance for forensic detection and analysis. Although the metabolism of individual SCs derived from 1-amino-3,3-dimethyl-1-oxobutan-2-yl (ADB-SCs) has been reported, their metabolites also undergo a continuous change and combination of their tail and core regions. Therefore, elucidating the metabolic characteristics and effects of these structures is essential to enhance our understanding. In this study, the human liver microsome was used as the model for studying the in vitro phase I metabolism of 12 ADB-SCs, and the metabolites obtained were analyzed using ultra-high performance liquid chromatography-tandem four-level rod-electrostatic field orbital ion trap mass spectrometry to determine type, structure, and relative contents. The results indicated that hydroxylation and N-dealkylation were the major metabolic pathways in 12 ADB-SCs. The effects of the core and tail on the metabolism of these ADB-SCs were studied using theoretical calculations. For N-dealkylation metabolism, the strong electron-withdrawing conjugative effect of the -N= moiety in the pyrazole ring, steric hindrance of the tail, and electronic effect of substituents on the tail significantly affected metabolism. Further, it changed the relative contents of N-dealkylation metabolites. For hydroxylation, the reaction types were inconsistent at different parts. For instance, the phenyl group of the core is electrophilic, and its electron cloud density determines whether the phenyl group can be hydroxylated at the specific metabolic sites. Meanwhile, hydroxylation of the neopentyl moiety of the linked group involves the oxidation of aliphatic C-H bonds, whereas amide-hydroxylamine tautomerism affects hydroxylation metabolism. When the alkyl chain in the tail contains functional groups (such as -F and >CC<), oxidative defluorination or dihydrodiol metabolites are produced. Taken together, we systematically determined d the effect of functional groups in the core and tail of ADB-SCs on their metabolism, validating confirmed the feasibility of ADB-SC metabolism prediction based on their structural characteristics.

A Highly Potent, Orally Bioavailable Pyrazole-Derived Cannabinoid CB2 Receptor- Selective Full Agonist for In Vivo Studies

The cannabinoid CB2 receptor (CB2R) is a potential therapeutic target for distinct forms of tissue injury and inflammatory diseases. To thoroughly investigate the role of CB2R in pathophysiological conditions and for target validation in vivo, optimal pharmacological tool compounds are essential. Despite the sizable progress in the generation of potent and selective CB2R ligands, pharmacokinetic parameters are often neglected for in vivo studies. Here, we report the generation and characterization of a tetra-substituted pyrazole CB2R full agonist named RNB-61 with high potency (K i 0.13-1.81 nM, depending on species) and a peripherally restricted action due to P-glycoprotein-mediated efflux from the brain. 3H and 14C labeled RNB-61 showed apparent K d values of <4 nM toward human CB2R in both cell and tissue experiments. The 6,800-fold selectivity over CB1 receptors and negligible off-targets in vitro, combined with high oral bioavailability and suitable systemic pharmacokinetic (PK) properties, prompted the assessment of RNB-61 in a mouse ischemia-reperfusion model of acute kidney injury (AKI) and in a rat model of chronic kidney injury/inflammation and fibrosis (CKI) induced by unilateral ureteral obstruction. RNB-61 exerted dose-dependent nephroprotective and/or antifibrotic effects in the AKI/CKI models. Thus, RNB-61 is an optimal CB2R tool compound for preclinical in vivo studies with superior biophysical and PK properties over generally used CB2R ligands.

Preparation of amphiphilic poly(divinylbenzene-co-N-vinylpyrrolidone)-functionalized polydopamine magnetic nanoadsorbents for enrichment of synthetic cannabinoids in wastewater

Concerns have been raised about synthetic cannabinoids (SCs), which are among the most often trafficked and used illegal substances. An analytical method that holds promise for determining illicit drug use in the general population is wastewater-based epidemiology (WBE). Unfortunately, the concentration of SCs in wastewater is often extremely low on account of their hydrophobic nature, thus presenting a significant obstacle to the accurate detection and quantification of SCs using WBE. In this study, we present novel magnetic nanomaterials as amphiphilic adsorbents for pretreatment of wastewater using magnetic solid phase extraction (MSPE). Polydopamine-modified Fe3O4 nanoparticles were used as the magnetic core and further functionalized with poly(divinylbenzene-N-vinylpyrrolidone). Coupled with UHPLC-MS/MS analysis, an analytical method to simultaneously detect nine SCs at trace-levels in wastewater was developed and validated, enriching 50 mL wastewater to 100 μL with limits of detection (LOD) being 0.005-0.5 ng L-1, limits of quantification (LOQ) being 0.01-1.0 ng L-1, recoveries ranging from 73.99 to 110.72%, and the intra- and inter-day precision's relative standard deviations less than 15%. In comparison to the time-consuming conventional column-based solid phase extraction, the entire MSPE procedure from sample pre-treatment to data acquisition could be finished in one hour, thus largely facilitating the WBE method for drug surveillance and control.

Structure-Activity Relationships, Deuteration, and Fluorination of Synthetic Cannabinoid Receptor Agonists Related to AKB48, 5F-AKB-48, and AFUBIATA

Synthetic cannabinoid receptor agonists (SCRAs) are a growing class of new psychoactive substances (NPS) commonly derived from an N-alkylated indole, indazole, or 7-azaindole scaffold. Diversification of this core (at the 3-position) with amide-linked pendant amino acid groups and modular N-alkylation (of the indole/indazole/7-azaindole core) ensures that novel SCRAs continue to enter the illicit drug market rapidly. In response to the large number of SCRAs that have been detected, pharmacological evaluation of this NPS class has become increasingly common. Adamantane-derived SCRAs have consistently appeared throughout the market since 2011, and as such, a systematic set of these derivatives was synthesized and pharmacologically evaluated. Deuterated and fluorinated adamantane derivatives were prepared to evaluate typical hydrogen bioisosteres, as well as evaluation of the newly detected AFUBIATA.

In vitro cannabinoid activity profiling of generic ban-evading brominated synthetic cannabinoid receptor agonists and their analogs

Following the enactment of a generic ban in China in 2021, the synthetic cannabinoid market has been evolving, now encompassing even wider structural diversity. Compounds carrying a brominated core such as ADB-5'Br-BUTINACA (ADMB-B-5Br-INACA) and tail-less analogs, such as ADB-5'Br-INACA (ADMB-5Br-INACA), MDMB-5'Br-INACA, and ADB-INACA (ADMB-INACA), have been detected since late 2021. This study investigated the cannabinoid receptor (CB) activation potential of synthesized (S)-enantiomers of these substances, as well as of two predicted analogs MDMB-5'Br-BUTINACA (MDMB-B-5Br-INACA) and ADB-5'F-BUTINACA (ADMB-B-5F-INACA), using CB1 and CB2 β-arrestin 2 recruitment assays and a CB1 intracellular calcium release assay. Surprisingly, the tail-less (S)-ADB-5'Br-INACA and (S)-MDMB-5'Br-INACA retained CB activity, albeit with a decreased potency compared to their tailed counterparts (S)-ADB-5'Br-BUTINACA and (S)-MDMB-5'Br-BUTINACA, respectively, which were potent and efficacious CB1 agonists. Also, at CB2, tail-less analogs showed a lower potency but increased efficacy. Removing the bromine substitution ((S)-ADB-INACA) resulted in a reduced activity at CB1; however, this effect was less prominent at CB2. Looking at tailed analogs, replacing the bromine with a fluorine substitution ((S)-ADB-5'F-BUTINACA) resulted in an increased potency and efficacy at both receptors. Furthermore, as ADB-5'Br-INACA and MDMB-5'Br-INACA have been frequently detected together in Scottish prisons, this study also evaluated the CB1 receptor activation potential of different mixtures of their respective reference standards, showing no unexpected cannabimimetic effect of combining both substances. Lastly, two powders seized by Belgian Customs and confirmed to contain ADB-5'Br-INACA and MDMB-5'Br-INACA, respectively, were assessed for CB activity. Based on the comparison with their reference standards, varying degrees of purity were suspected.

Synthesis and Functional Evaluation of Synthetic Cannabinoid Receptor Agonists Related to ADB-HEXINACA

ADB-HEXINACA has been recently reported as a synthetic cannabinoid receptor agonist (SCRA), one of the largest classes of new psychoactive substances (NPSs). This compound marks the entry of the n-hexyl tail group into the SCRA landscape, which has continued in the market with recent, newly detected SCRAs. As such, a proactive characterization campaign was undertaken, including the synthesis, characterization, and pharmacological evaluation of ADB-HEXINACA and a library of 41 closely related analogues. Two in vitro functional assays were employed to assess activity at CB1 and CB2 cannabinoid receptors, measuring Gβγ-coupled agonism through a fluorescence-based membrane potential assay (MPA) and β-arrestin 2 (βarr2) recruitment via a live cell-based nanoluciferase complementation reporter assay. ADB-HEXINACA was a potent and efficacious CB1 agonist (CB1 MPA pEC50 = 7.87 ± 0.12 M; Emax = 124 ± 5%; βarr2 pEC50 = 8.27 ± 0.14 M; Emax = 793 ± 42.5), as were most compounds assessed. Isolation of the heterocyclic core and alkyl tails allowed for the comprehensive characterization of structure-activity relationships in this compound class, which were rationalized in silico via induced fit docking experiments. Overall, most compounds assessed are possibly emerging NPSs.

Changing trends in novel benzodiazepine use within Scottish prisons: detection, quantitation, prevalence, and modes of use

Drug use within prisons is increasingly complex and unpredictable. Benzodiazepines are currently one of the most common drugs detected in individuals leaving Scottish prisons; however, understanding illicit benzodiazepine use within prisons and assessing the potential harm to individuals is challenging due to the lack of available analytical data on the substances circulating. Increasingly, materials, such as paper and clothing, infused with novel benzodiazepines have been identified as a smuggling route into Scottish prisons. Methods were developed for the qualitative and quantitative analysis of benzodiazepines using gas chromatography-mass spectrometry (GC-MS) and applied to 495 seized samples from 11 Scottish prisons, including papers, cards, blotters, powders, tablets, and clothing. Evolution in the benzodiazepines being detected was demonstrated, with etizolam being the most prevalent throughout 2020/2021 following which flubromazepam and bromazolam detections increased. Additionally, significant changes in the smuggling methods and drug formats detected occurred over time following policy changes within prisons. These data represent the first reported widescale etizolam quantitation data and demonstrate high levels of variability across all sample types, most notably within tablets (0.34-2.33 mg per tablet). Additionally, concentration mapping of a whole seized card sample revealed the total concentration of drug present (312.5 mg) and demonstrated variability across the surface of the card (1.16-1.87 mg/cm2). These data highlight the challenges of consistent dosing for individuals and the high risks of unintentional overdose. Increased understanding of the challenge of such drug smuggling and benzodiazepine use will aid in the development of strategies to reduce supply and mitigate harm.

A highly potent, orally bioavailable pyrazole-derived cannabinoid CB2 receptor-selective full agonist for in vivo studies

The cannabinoid CB2 receptor (CB2R) is a potential therapeutic target for distinct forms of tissue injury and inflammatory diseases. To thoroughly investigate the role of CB2R in pathophysiological conditions and for target validation in vivo, optimal pharmacological tool compounds are essential. Despite the sizable progress in the generation of potent and selective CB2R ligands, pharmacokinetic parameters are often neglected for in vivo studies. Here, we report the generation and characterization of a tetra-substituted pyrazole CB2R full agonist named RNB-61 with high potency (K i 0.13-1.81 nM, depending on species) and a peripherally restricted action due to P-glycoprotein mediated efflux from the brain. 3H and 14C labelled RNB-61 showed apparent K d values < 4 nM towards human CB2R in both cell and tissue experiments. The >6000-fold selectivity over CB1 receptors and negligible off-targets in vitro, combined with high oral bioavailability and suitable systemic pharmacokinetic (PK) properties, prompted the assessment of RNB-61 in a mouse ischemia-reperfusion model of acute kidney injury (AKI) and in a rat model of chronic kidney injury/inflammation and fibrosis (CKI) induced by unilateral ureteral obstruction. RNB-61 exerted dose-dependent nephroprotective and/or antifibrotic effects in the AKI/CKI models. Thus, RNB-61 is an optimal CB2R tool compound for preclinical in vivo studies with superior biophysical and PK properties over generally used CB2R ligands.

In vitro cannabinoid receptor activity, metabolism, and detection in seized samples of CH-PIATA, a new indole-3-acetamide synthetic cannabinoid

The rapidly evolving synthetic cannabinoid receptor agonist (SCRA) market poses significant challenges for forensic scientists. Since the enactment of a generic ban in China, a variety of new compounds have emerged capable of evading the legislation by carrying new structural features. One recent example of a SCRA with new linker and head moieties is CH-PIATA (CH-PIACA, CHX-PIATA, CHX-PIACA). CH-PIATA bears an additional methylene spacer in the linker moiety between the indole core and the traditional carbonyl component of the linker. This study describes detections in 2022 of this new SCRA in the United States, Belgium, and Scottish prisons. CH-PIATA was detected once in a seized powder by Belgian customs and 12 times in Scottish prisons in infused papers or resin. The metabolites of CH-PIATA were investigated via in vitro human liver microsome (HLM) incubations and eight metabolites were identified, dominated by oxidative biotransformations. A blood sample from the United States was confirmed to contain a mixture of SCRAs including CH-PIATA via presence of the parent and at least five of the metabolites identified from HLM incubations. Furthermore, this paper evaluates the intrinsic in vitro cannabinoid 1 and 2 (CB1 and CB2) receptor activation potential of CH-PIATA reference material and the powder seized by Belgian customs by means of β-arrestin 2 recruitment assays. Both the reference and the seized powder showed a weak activity at both CB receptors with signs of antagonism found. Based on these results, the expected harm potential of this newly emerging substance remains limited.

Synthesis, characterization and differentiation of the structural isomers of valine and tert-leucine derived synthetic cannabinoids

The identification of the synthetic cannabinoids receptor agonists (SCRAs) has always posed a great challenge to drug testing laboratories with slight structural modifications aimed at evading drug legislation. In addition, the most prevalent synthetic cannabinoids have valine and tert-leucine amino acid moieties where re-arrangement of the carbon chains can result in structural isomers that are very similar to the parent synthetic cannabinoids. This makes their analysis and identification challenging, and the problem is compounded with the difficulty in purchasing reference standards quickly and a lack of literature for comparison. Therefore, in this investigation, four series of synthetic cannabinoids (AB-PINACA, AB-CHMINACA, MMB-FUBINACA and 5-fluoro-MDMB-PINACA) and their alkyl chain structural isomers at the amino acid moieties were synthesized and characterized using various analytical techniques-gas chromatography-mass spectrometry (GC-MS), gas chromatography-infrared detection (GC-IRD) and nuclear magnetic resonance (NMR) spectroscopy to evaluate the ability of each analytical technique to differentiate the respective isomers for their identification. A total of 12 isomers were synthesized and analysed together with the four parent synthetic cannabinoids. NMR was able to differentiate between all the compounds, whereas GC-IRD was able to discern between most of the synthetic cannabinoids and their isomers. GC-MS had the least discriminating power and was not able to differentiate some of the compounds that has very similar mass spectra. The results from this work will be useful to other drug testing laboratories that are facing the identification of related synthetic cannabinoids.

The synthetic cannabinoid 5-fluoro ABICA upregulates angiogenic markers and stimulates tube formation in human brain microvascular endothelial cells

Objective

Synthetic cannabinoids (SCs), a class of psychoactive compounds emulating the effects of natural cannabis, have prompted addiction and psychosis concerns. However, recent research has suggested potential pharmacological applications, particularly in brain angiogenesis-an essential physiological process for growth, repair, and tissue maintenance, in which new blood vasculature is formed from existing vasculature. This study explored the in vitro ability of the SC 5-fluoro ABICA to enhance new blood formation processes in human brain microvascular endothelial cells (HBMECs).

Methods

HBMECs were treated with various concentrations of 5-fluoro ABICA (1 μM, 0.1 μM, 0.01 μM, 0.001 μM, and 0.0001 μM). A comprehensive analysis was conducted, including MTT assays indicating cell viability, wound healing assays indicating migration ability, and tube formation assays indicating the angiogenesis potential of endothelial cells. Additionally, mRNA expression and protein levels of specific pro-angiogenic factors were measured, and the phosphorylation levels of glycogen synthase kinase-3β were detected in treated HBMECs through ELISA, real-time PCR, and western blotting.

Results

Treatment with 5-fluoro ABICA effectively stimulated proliferation, migration, and tube formation in HBMECs in a dose-dependent manner; markedly increased the expression of pro-angiogenic factors; and upregulated levels of phosphorylated-GSK-3β.

Conclusion

Our findings demonstrate that 5-fluoro ABICA stimulates angiogenesis in endothelial cells, thus potentially offering therapeutic options for diseases associated with angiogenesis. However, further research is needed to fully understand the molecular mechanism of 5-fluoro ABICA in angiogenesis, including ethical considerations regarding its use in medical research.

Detection in seized samples, analytical characterization, and in vitro metabolism of the newly emerged 5-bromo-indazole-3-carboxamide synthetic cannabinoid receptor agonists

Synthetic cannabinoid receptor agonists (SCRAs) are a diverse class of new psychoactive substances (NPS) and new structural scaffolds have emerged on the recreational drug market since the enactment of Chinese SCRA analog controls in 2021. This study reports the first SCRAs to be detected with a bromide at the 5 position (5'Br) on the phenyl ring of the indazole core and without a tail moiety. ADB-5'Br-INACA (ADMB-5'Br-INACA) and MDMB-5'Br-INACA were detected in seized samples from Scottish prisons, Belgian customs, and US forensic casework. The brominated analog with a tail moiety, ADB-5'Br-BUTINACA (ADMB-5'Br-BUTINACA), was also detected in Scottish prisons and US forensic casework. The metabolites of these compounds and the predicted compound MDMB-5'Br-BUTINACA were identified through incubation with primary human hepatocytes to aid in their toxicological identification. The bromide on the indazole remains intact on metabolites, allowing these compounds to be easily distinguished in toxicological samples from their non-brominated analogs. Glucuronidation was more common for tail-less analogs than their butyl tail-containing counterparts. Forensic toxicologists are advised to update their analytical methods with the characteristic ions for these compounds, as well as their anticipated urinary markers: amide hydrolysis and monoOH at tert-butyl metabolites (after β-glucuronidase treatment) for ADB-5'Br-INACA; monoOH at tert-butyl and amide hydrolysis metabolites for ADB-5'Br-BUTINACA; and ester hydrolysis metabolites with additional metabolites for MDMB-5'Br-INACA and MDMB-5'Br-BUTINACA. Toxicologists should remain vigilant to the emergence of new SCRAs with halogenation of the indazole core and tail-less analogs, which have already started to emerge.

Nontargeted screening based on EI-MS spectra using statistical methods: An investigative study of synthetic indole/indazole cannabinoids

RATIONALE

Mass spectrometry has evolved into a highly powerful tool for qualitative and quantitative chemical analyses. However, the identification of trace amounts of previously unknown structures in complex chemical matrix environments remains challenging. The rapid emergence of new synthetic cannabinoid substances is a typical example of this. Existing laboratory techniques are mostly based on methods used for lists of known illegal compounds. This situation poses a challenge to traditional data analysis and the risk of missing the compounds. Therefore, we propose to develop and validate a statistical model to classify newly emerging synthetic cannabinoid substances into a structural class or subclass.

METHODS

We obtained 70 electrospray ionization spectra of indole/indazole synthetic cannabinoids from both the actual standard analysis and the SWGDRUG mass spectral library (version 3.10). Each sample consisted of 330 m/z variables and corresponding relative intensities. We first cleared the variables with a variance below 0.1. Principal component analysis (PCA) was performed on the variance-filtered data, and the two principal components were retained to generate new data for hierarchical clustering. After hierarchical clustering, we used the receiver operating characteristic method in this cluster.

RESULTS

Seventy synthetic indole/indazole cannabinoids were classified into four clusters. The side chain of cluster 1 is mainly fluorobenzyl, cluster 2 is pentyl, cluster 3 includes compounds from several structures, and cluster 4 is mainly fluoropentyl. The most relevant characteristic ions are m/z 109, m/z 252, and m/z 253 for cluster 1; m/z 144 and m/z 214 for cluster 2; and m/z 232 and m/z 233 for cluster 4.

CONCLUSIONS

This study provides a more objective and less time-consuming solution for characterizing synthetic cannabinoids. And this work validates the ability of PCA to extract characteristic fragment ions.

A subtle structural modification of a synthetic cannabinoid receptor agonist drastically increases its efficacy at the CB1 receptor

The emergence of synthetic cannabinoid receptor agonists (SCRAs) as illicit psychoactive substances has posed considerable public health risks that include fatalities. Many SCRAs exhibit much higher efficacy and potency, compared with the phytocannabinoid Δ9-tetrahydrocannabinol (THC), at the cannabinoid receptor 1 (CB1R), a G protein-coupled receptor involved in modulating neurotransmitter release. In this study, we investigated structure activity relationships (SAR) of aminoalkylindole SCRAs at CB1Rs, focusing on 5F-pentylindoles containing an amide linker attached to different head moieties. Using in vitro bioluminescence resonance energy transfer (BRET) assays, we identified a few of SCRAs exhibiting significantly higher efficacy in engaging the Gi protein and recruiting β-arrestin than the reference CB1R full agonist CP55940. Importantly, adding a methyl group at the head moiety of 5F-MMB-PICA yielded 5F-MDMB-PICA, an agonist exhibiting a large increase in efficacy and potency at the CB1R. This pharmacological observation was supported by a functional assay of the effects of these SCRAs on glutamate field potentials recorded in hippocampal slices. Molecular modeling and simulations of the CB1R bound with either of the SCRAs revealed critical structural determinants contributing to the higher efficacy of 5F-MDMB-PICA, and how these subtle differences propagated to the receptor-G protein interface. Thus, we find that apparently minor structural changes in the head moiety of SCRAs can cause major changes in efficacy. Our results highlight the need for close monitoring of structural modifications of newly emerging SCRAs and their potential for toxic drug responses in humans.

Recreational cannabis: Profile of cannabinoids present in marijuana samples supplied by the consuming population

As cannabis/marijuana is one of the most consumed psychoactive substances in the world, knowing the composition and type of cannabis sold in urban environments is a necessary input for the design of public health policies based on scientific evidence. This study characterized the main phytocannabinoids of marijuana samples (cigarettes or buds) obtained in urban and rural areas of the city of Medellín in October 2021. Non-probabilistic convenience sampling was carried out in which 87 marijuana samples donated by consumers were collected at different collection points throughout the city, and gas chromatography-mass spectrometry and flame ionization techniques were employed for the characterization of phytocannabinoids. Tetrahydrocannabinol (THC) was found to be the main constituent of circulating marijuana in Medellín, where 67.8% of the samples had a high or higher toxicological range for THC; the foregoing in a context where the deregulated market in practice limits the possibility that consumers have to calibrate or decide the concentration of cannabinoids in their doses.

Comprehensive Characterization of a Systematic Library of Alkyl and Alicyclic Synthetic Cannabinoids Related to CUMYL-PICA, CUMYL-BUTICA, CUMYL-CBMICA, and CUMYL-PINACA

Over 200 synthetic cannabinoid receptor agonists (SCRAs) have been identified as new psychoactive substances. Effective monitoring and characterization of SCRAs are hindered by the rapid pace of structural evolution. Ahead of possible appearance on the illicit drug market, new SCRAs were synthesized to complete a systematic library of cumyl-indole- (e.g., CUMYL-CPrMICA, CUMYL-CPMICA) and cumyl-indazole-carboxamides (e.g., CUMYL-CPrMINACA, CUMYL-CPMINACA), encompassing butyl, pentyl, cyclopropylmethyl, cyclobutylmethyl, cyclopentylmethyl, and cyclohexylmethyl tails. Comprehensive pharmacological characterization was performed with three assay formats, monitoring the recruitment of either wild-type or C-terminally truncated (βarr2d366) β-arrestin2 to the activated cannabinoid 1 receptor (CB₁) or monitoring G_βγ-mediated membrane hyperpolarization. Altered compound characterization was observed when comparing derived potency (EC₅₀) and efficacy (E_max) values from both assays monitoring the same or a different signaling event, whereas ranges and ranking orders were similar. Structure-activity relationships (SAR) were assessed in threefold, resulting in the identification of the pendant tail as a critical pharmacophore, with the optimal chain length for CB₁ activation approximating an n-pentyl (e.g., cyclopentylmethyl or cyclohexylmethyl tail). The activity of the SCRAs encompassing cyclic tails decreased with decreasing number of carbons forming the cyclic moiety, with CUMYL-CPrMICA showing the least CB₁ activity in all assay formats. The SARs were rationalized via molecular docking, demonstrating the importance of the optimal steric contribution of the hydrophobic tail. While SAR conclusions remained largely unchanged, the differential compound characterization by both similar and different assay designs emphasizes the importance of detailing specific assay characteristics to allow adequate interpretation of potencies and efficacies.

Trends in hospital presentations following analytically confirmed synthetic cannabinoid receptor agonist exposure before and after implementation of the 2016 UK Psychoactive Substances Act

BACKGROUND AND AIMS

The United Kingdom (UK) Psychoactive Substances Act (PSA), implemented on the 26^th  May 2016, made the production, supply and sale of all non-exempted psychoactive substances illegal. The aim of this study was to measure trends in hospital presentations for severe toxicity following analytically confirmed synthetic cannabinoid receptor agonist (SCRA) exposure before and after implementation of the PSA.

DESIGN

Observational study.

SETTING

Thirty-four hospitals across the UK participating in the Identification of Novel Psychoactive Substances (IONA) study.

PARTICIPANTS

A total of 627 (79.9% male) consenting individuals who presented to participating hospitals between July 2015 and December 2019 with severe acute toxicity and suspected novel psychoactive substances exposure.

MEASUREMENTS

Toxicological analyses of patient samples were conducted using liquid-chromatography tandem mass-spectrometry. Time-series analysis was conducted on the monthly number of patients with and without analytically confirmed SCRA exposure using Poisson segmented regression.

FINDINGS

SCRAs were detected in 35.7% (n = 224) of patients. After adjusting for seasonality and the number of active sites, models showed no clear evidence of an upward or downward trend in the number of SCRA exposure cases in the period before (incidence rate ratio [IRR], 1.12; 95% CI, 0.99-1.26; P = 0.068) or after (IRR, 0.97; 95% CI, 0.94-1.01; P = 0.202) the implementation of the PSA. There was also no clear evidence of an upward or downward trend in non-SCRA exposure cases before (IRR, 1.12; 95% CI, 0.98-1.27; P = 0.105) or after (IRR, 1.01; 95% CI, 0.98-1.04; P = 0.478) implementation of the PSA.

CONCLUSIONS

There is no clear evidence of an upward or downward trend in the number of patients presenting to UK hospitals with severe acute toxicity following analytically confirmed synthetic cannabinoid receptor agonist exposure since the implementation of the Psychoactive Substances Act.

In vitro and in vivo pharmacology of nine novel synthetic cannabinoid receptor agonists

Synthetic cannabinoid receptor agonists (SCRAs) are novel psychoactive substances that bind to and activate CB1 receptors in the brain. The structural manipulations observed in newer SCRAs suggest that manufacturers have incorporated modern drug development techniques into their repertoire, often producing higher CB1 receptor affinity than Δ9-tetrahydrocannabinol (Δ9-THC). This study examined nine SCRAs recently detected by forensic surveillance, some of which caused fatalities: 5F-MDMB-PICA, FUB-144, 5F-MMB-PICA, MMB-4en-PICA, MMB-FUBICA, 5F-EDMB-PINACA, APP-BINACA, MDMB-4en-PINACA, and FUB-AKB48. Compounds were evaluated for CB1 and CB2 receptor binding affinity and functional activation and for their effects on body temperature, time course, and pharmacological equivalence with Δ9-THC in Δ9-THC drug discrimination in mice. All SCRAs bound to and activated CB1 and CB2 receptors with high affinity, with similar or greater affinity for CB2 than CB1 receptors and stimulated [35S]GTPγS binding in CB1 and CB2 expressing cell membranes. All compounds produced hypothermia, with shorter latency to peak effects for SCRAs than Δ9-THC. All SCRAs fully substituted for Δ9-THC in drug discrimination at one or more doses. Rank order potency in producing in vivo effects mostly aligned with rank order CB1 receptor affinities. Potencies for Δ9-THC-like discriminative stimulus effects were similar across sex except Δ9-THC was more potent in females and 5F-MMB-PICA was more potent in males. In summary, 5F-EMDB-PINACA, 5F-MDMB-PICA, MDMB-4en-PINACA, FUB-144, FUB-AKB48, 5F-MMB-PICA, MMB-4en-PICA, and MMB-FUBICA are potent and efficacious SCRAs with pharmacology like that of past SCRAs that have been abused in humans. In contrast, APP-BINACA was efficacious, but had lower potency than most past SCRAs.

Linking in vitro and ex vivo CB1 activity with serum concentrations and clinical features in 5F-MDMB-PICA users to better understand SCRAs and their metabolites

Synthetic cannabinoid receptor agonists (SCRAs) pose a danger to public health. This study focused on individuals experiencing recreational drug toxicity who had used 5F-MDMB-PICA.Patient records were evaluated regarding vital signs, Glasgow Coma Scale (GCS) and clinical features. Liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) confirmed and quantified the presence of 5F-MDMB-PICA (and/or metabolites) as the only SCRA present in the serum of 71 patients. Cannabinoid activity was evaluated by a cannabinoid receptor (CB₁) bioassay, to assess the relationship between serum concentrations and ex vivo human CB₁ activation potential. Furthermore, a link with the clinical presentation was appraised.5F-MDMB-PICA and five metabolites were pharmacologically profiled in vitro, revealing theoretically possible contributions of two active in vivo metabolites to overall cannabinoid activity. Serum concentrations of 5F-MDMB-PICA were correlated to the ex vivo cannabinoid activity, revealing a sigmoidal relationship. The latter could also be predicted based on pharmacological characterization of 5F-MDMB-PICA and its metabolites and an in-depth investigation of the bioassay outcome. Clinically, the GCS showed a significant trend (decrease) with increasing ex vivo cannabinoid activity.This is the first study to evaluate possible toxic effects of 5F-MDMB-PICA in a unique large patient cohort. It allows a better understanding of 5F-MDMB-PICA and metabolites in humans, suggesting a negligible contribution by 5F-MDMB-PICA metabolites to the overall cannabinoid activity in serum. Additionally, this work shows that in vitro pharmacological characterization allows close prediction of an individual's ex vivo CB₁ activity, the latter showing a relationship with the level of consciousness.

Going deeper into the toxicokinetics of synthetic cannabinoids: in vitro contribution of human carboxylesterases

Synthetic cannabinoids (SC) are new psychoactive substances known to cause intoxications and fatalities. One reason may be the limited data available concerning the toxicokinetics of SC, but toxicity mechanisms are insufficiently understood so far. Human carboxylesterases (hCES) are widely known to play a crucial role in the catalytic hydrolysis of drugs (of abuse). The aim of this study was to investigate the in vitro contribution of hCES to the metabolism of the 13 SC 3,5-AB-5F-FUPPYCA, AB-5F-P7AICA, A-CHMINACA, DMBA-CHMINACA, MBA-CHMINACA, MDMB-4F-BINACA, MDMB-4en-PINACA, MDMB-FUBICA, MDMB-5F-PICA, MMB-CHMICA, MMB-4en-PICA, MMB-FUBINACA, and MPhP-5F-PICA. The SC were incubated with recombinant hCES1b, hCES1c, or hCES2 and analyzed by liquid chromatography-ion trap mass spectrometry to assess amide or ester hydrolysis in an initial activity screening. Enzyme kinetic studies were performed if sufficient hydrolysis was observed. No hydrolysis of the amide linker was observed using those experimental conditions. Except for MDMB-5F-PICA, ester hydrolysis was always detected if an ester group was present in the head group. In general, SC with a terminal ester bearing a small alcohol part and a larger acyl part showed higher affinity to hCES1 isozymes. Due to the low hydrolysis rates, enzyme kinetics could not be modeled for the SC with a tert-leucine-derived moiety, but hydrolysis reactions of MPhP-5F-PICA and of those containing a valine-derived moiety followed classic Michaelis-Menten kinetics. In conclusion, drug-drug/drug-food interactions or hCES polymorphisms may prolong the half-life of SC and the current results help to estimate the risk of toxicity in the future after combining them with activity and clinical data.

Cannabimimetic effects of abused indazole-carboxamide synthetic cannabinoid receptor agonists AB-PINACA, 5F-AB-PINACA and 5F-ADB-PINACA in mice: Tolerance, dependence and withdrawal

BACKGROUND

Chronic abuse of synthetic cannabinoid receptor agonists (SCRAs), known as "K2″ or "Spice", threatens public health and safety. Recently, SCRAs of the indazole-carboxamide structural class have become more prevalent. Preclinical studies investigating the tolerance and dependence potentially involved in chronic SCRA abuse is limited. The present study determined the in vivo effects of chronic exposure to indazole-carboxamide SCRAs, AB-PINACA, 5F-AB-PINACA and 5F-ADB-PINACA compared to the first-generation SCRA, JWH-018.

METHODS

Adult male C57Bl/6 mice were used for dose-effect determinations of hypothermic effects. Adult male NIH Swiss mice were used in biotelemetry studies to assess tolerance to hypothermic effects following repeated SCRA administration over 5 consecutive days, and to determine the role of Phase I drug metabolism via acute CYP450 inhibition in the presence of 1-ABT, a nonspecific CYP450 inhibitor. SCRA dependence was determined in adult male NIH Swiss mice via assessment of rimonabant-precipitated observable sign of withdrawal (i.e., front paw tremors).

RESULTS

All SCRAs elicited dose-dependent hypothermia mediated through cannabinoid CB1 receptors (CB1Rs). 1-ABT increased duration of hypothermia for all SCRAs tested, and increased the magnitude of hypothermia for all SCRAs except 5F-ADB-PINACA. Upon repeated administration, tolerance to hypothermic effects of AB-PINACA, 5F-AB-PINACA and 5F-ADB-PINACA was much less than that of JWH-018. Similarly, rimonabant-precipitated front paw tremors were much less frequent in mice treated with 5F-AB-PINACA and 5F-ADB-PINACA than in mice treated with JWH-018.

CONCLUSIONS

These findings suggest a decreased potential for tolerance and withdrawal among indazole-carboxamide SCRAs, and may imply structural class-dependent profiles of in vivo effects among SCRAs.

Putative Synthetic Cannabinoids MEPIRAPIM, 5F-BEPIRAPIM (NNL-2), and Their Analogues Are T-Type Calcium Channel (CaV3) Inhibitors

Synthetic cannabinoid receptor agonists (SCRAs) are a large and growing class of new psychoactive substances (NPSs). Two recently identified compounds, MEPIRAPIM and 5F-BEPIRAPIM (NNL-2), have not been confirmed as agonists of either cannabinoid receptor subtype but share structural similarities with both SCRAs and a class of T-type calcium channel (Ca_V3) inhibitors under development as new treatments for epilepsy and pain. In this study, MEPIRAPIM and 5F-BEPIRAPIM and 10 systematic analogues were synthesized, analytically characterized, and pharmacologically evaluated using in vitro cannabinoid receptor and Ca_V3 assays. Several compounds showed micromolar affinities for CB₁ and/or CB₂, with several functioning as low potency agonists of CB₁ and CB₂ in a membrane potential assay. 5F-BEPIRAPIM and four other derivatives were identified as potential Ca_V3 inhibitors through a functional calcium flux assay (>70% inhibition), which was further confirmed using whole-cell patch-clamp electrophysiology. Additionally, MEPIRAPIM and 5F-BEPIRAPIM were evaluated in vivo using a cannabimimetic mouse model. Despite detections of MEPIRAPIM and 5F-BEPIRAPIM in the NPS market, only the highest MEPIRAPIM dose (30 mg/kg) elicited a mild hypothermic response in mice, with no hypothermia observed for 5F-BEPIRAPIM, suggesting minimal central CB₁ receptor activity.

Defining Steric Requirements at CB1 and CB2 Cannabinoid Receptors Using Synthetic Cannabinoid Receptor Agonists 5F-AB-PINACA, 5F-ADB-PINACA, PX-1, PX-2, NNL-1, and Their Analogues

Synthetic cannabinoid receptor agonists (SCRAs) are a diverse class of new psychoactive substances (NPS). They commonly comprise N-alkylated indole, indazole, or 7-azaindole scaffolds with amide-linked pendant amino acid groups. To explore the contribution of the amino acid side chain to the cannabinoid pharmacology of SCRA NPS, a systematic library of side chain-modified SCRAs was prepared based on the recent detections of amino acid derivatives 17 (5F-AB-PINACA), 18 (5F-ADB-PINACA), 15 (PX-1), 19 (PX-2), and 20 (NNL-1). In vitro binding affinities and functional activities at cannabinoid type 1 and 2 receptors (CB₁ and CB₂, respectively) were determined for all the library members using radioligand competition experiments and a fluorescence-based membrane potential assay. Binding affinities and functional activities varied widely across compounds (K_i = 0.32 to >10 000 nM, EC₅₀ = 0.24-1259 nM), with several clear structure-activity relationships (SARs) emerging. Affinity and potency at CB₁ changed as a function of the heterocyclic core (indazole > indole > 7-azaindole) and the pendant amino acid side chain (tert-butyl > iso-propyl > iso-butyl > benzyl > ethyl > methyl > hydrogen). Ensemble docking at CB₁ revealed a clear steric basis for observed SAR trends. Interestingly, although 15 (PX-1) and 19 (PX-2) have been detected in recreational drug markets, they failed to induce centrally CB₁-mediated effects (e.g., hypothermia) in mice using radiobiotelemetry. Together, these data provide insights regarding structural contributions to the cannabimimetic profiles of 17 (5F-AB-PINACA), 18 (5F-ADB-PINACA), 15 (PX-1), 19 (PX-2), 20 (NNL-1), and other SCRA NPS.

Structure-activity relationships for 5F-MDMB-PICA and its 5F-pentylindole analogs to induce cannabinoid-like effects in mice

Synthetic cannabinoid receptor agonists (SCRAs) are an evolving class of new psychoactive substances found on recreational drug markets worldwide. The indole-containing compound, 5F-MDMB-PICA, is a popular SCRA associated with serious medical consequences, including overdose and hospitalizations. In vitro studies reveal that 5F-MDMB-PICA is a potent agonist at cannabinoid type 1 receptors (CB₁), but little information exists regarding in vivo pharmacology of the drug. To this end, we examined the in vitro and in vivo cannabinoid-like effects produced by 5F-MDMB-PICA and related 5F-pentylindole analogs with differing composition of the head group moiety (i.e., 5F-NNEI, 5F-SDB-006, 5F-CUMYL-PICA, 5F-MMB-PICA). In mouse brain membranes, 5F-MDMB-PICA and its analogs inhibited binding to [³H]rimonabant-labeled CB₁ and displayed agonist actions in [³⁵S]GTPγS functional assays. 5F-MDMB-PICA exhibited the highest CB₁ affinity (K_i = 1.24 nM) and functional potency (EC₅₀ = 1.46 nM), but head group composition markedly influenced activity in both assays. For example, the 3,3-dimethylbutanoate (5F-MDMB-PICA) and cumyl (5F-CUMYL-PICA) head groups engendered high CB₁ affinity and potency, whereas a benzyl (5F-SDB-006) head group did not. In C57BL/6J mice, all 5F-pentylindole SCRAs produced dose- and time-dependent hypothermia, catalepsy, and analgesia that were reversed by rimonabant, indicating CB₁ involvement. In vitro K_i and EC₅₀ values were positively correlated with in vivo ED₅₀ potency estimates. Our findings demonstrate that 5F-MDMB-PICA is a potent SCRA, and subtle alterations to head group composition can have profound influence on pharmacological effects at CB₁. Importantly, measures of CB₁ binding and efficacy in mouse brain tissue seem to accurately predict in vivo drug potency in this species.

Quantifying the Kinetics of Signaling and Arrestin Recruitment by Nervous System G-Protein Coupled Receptors

Neurons integrate inputs over different time and space scales. Fast excitatory synapses at boutons (ms and μm), and slow modulation over entire dendritic arbors (seconds and mm) are all ultimately combined to produce behavior. Understanding the timing of signaling events mediated by G-protein-coupled receptors is necessary to elucidate the mechanism of action of therapeutics targeting the nervous system. Measuring signaling kinetics in live cells has been transformed by the adoption of fluorescent biosensors and dyes that convert biological signals into optical signals that are conveniently recorded by microscopic imaging or by fluorescence plate readers. Quantifying the timing of signaling has now become routine with the application of equations in familiar curve fitting software to estimate the rates of signaling from the waveform. Here we describe examples of the application of these methods, including (1) Kinetic analysis of opioid signaling dynamics and partial agonism measured using cAMP and arrestin biosensors; (2) Quantifying the signaling activity of illicit synthetic cannabinoid receptor agonists measured using a fluorescent membrane potential dye; (3) Demonstration of multiplicity of arrestin functions from analysis of biosensor waveforms and quantification of the rates of these processes. These examples show how temporal analysis provides additional dimensions to enhance the understanding of GPCR signaling and therapeutic mechanisms in the nervous system.

Synthesis and pharmacological evaluation of newly detected synthetic cannabinoid receptor agonists AB-4CN-BUTICA, MMB-4CN-BUTINACA, MDMB-4F-BUTICA, MDMB-4F-BUTINACA and their analogs

Synthetic cannabinoid receptor agonists (SCRAs) continue to make up a significant portion new psychoactive substances (NPS) detected and seized worldwide. Due to their often potent activation of central cannabinoid receptors in vivo, use of SCRAs can result in severe intoxication, in addition to other adverse health effects. Recent detections of AB-4CN-BUTICA, MMB-4CN-BUTINACA, MDMB-4F-BUTICA and MDMB-4F-BUTINACA mark a continuation in the appearance of SCRAs bearing novel tail substituents. The proactive characterization campaign described here has facilitated the detection of several new SCRAs in toxicological case work. Here we detail the synthesis, characterization, and pharmacological evaluation of recently detected SCRAs, as well as a systematic library of 32 compounds bearing head, tail, and core group combinations likely to appear in future. In vitro radioligand binding assays revealed most compounds showed moderate to high affinity at both CB₁ (pK _i = < 5 to 8.89 ± 0.09 M) and CB₂ (pK _i = 5.49 ± 0.03 to 9.92 ± 0.09 M) receptors. In vitro functional evaluation using a fluorescence-based membrane potential assay showed that most compounds were sub-micromolar to sub-nanomolar agonists at CB₁ (pEC₅₀ = < 5 to 9.48 ± 0.14 M) and CB₂ (pEC₅₀ = 5.92 ± 0.16 to 8.64 ± 0.15 M) receptors. An in silico receptor-ligand docking approach was utilized to rationalize binding trends for CB₂ with respect to the tail substituent, and indicated that rigidity in this region (i.e., 4-cyanobutyl) was detrimental to affinity.

NNL-3: A Synthetic Intermediate or a New Class of Hydroxybenzotriazole Esters with Cannabinoid Receptor Activity?

Synthetic cannabinoid receptor agonists (SCRAs) remain a prolific class of new psychoactive substances (NPS) and continue to expand rapidly. Despite the recent identification of hydroxybenzotriazole (HOBt) containing SCRAs in synthetic cannabis samples, there is currently no information regarding the pharmacological profile of these NPS with respect to human CB₁ and CB₂ receptors. In the current study, a series consisting of seven HOBt indole-, indazole-, and 7-azaindole-carboxylates bearing a range of N-alkyl substituents were synthesized and pharmacologically evaluated. Competitive binding assays at CB₁ and CB₂ demonstrated that all analogues except a 2-methyl-substituted derivative had low affinity for CB₁ (K_i = 3.80-43.7 μM) and CB₂ (K_i = 2.75-18.2 μM). A fluorometric functional assay revealed that 2-methylindole- and indole-derived HOBt carboxylates were potent and efficacious agonists of CB₁ (EC₅₀ = 12.0 and 63.7 nM; E_max = 118 and 120%) and CB₂ (EC₅₀ = 10.9 and 321 nM; E_max = 91 and 126%). All other analogues incorporating indazole and 7-azaindole cores and bearing a range of N1-substituents showed relatively low potency for CB₁ and CB₂. Additionally, a reporter assay monitoring β-arrestin 2 (βarr2) recruitment to the receptor revealed that the 2-methylindole example was the most potent and efficacious at CB₁ (EC₅₀ = 131 nM; E_max = 724%) and the most potent at CB₂ (EC₅₀ = 38.2 nM; E_max = 51%). As with the membrane potential assay, the indazole and other indole HOBt carboxylates were considerably less potent at both receptors, and analogues comprising a 7-azaindole core showed little activity. Taken together, these data suggest that NNL-3 demonstrates little CB1 receptor activity and is unlikely to be psychoactive in humans. NNL-3 is likely an unintended SCRA manufacturing byproduct. However, the synthesis of NNL-3 analogues proved simple and general, and some of these showed potent cannabimetic profiles in vitro, indicating that HOBt esters of this type may represent an emerging class of SCRA NPS.

"Walking the nitrogen around the ring": Chemical synthesis and spectroscopic characterization of novel 4-, 5-, 6-, and 7-azaindazole analogs of the synthetic cannabinoid receptor agonist MDMB-PINACA

Over the past decade, synthetic cannabinoid receptor agonists (SCRAs) have rapidly evolved to encompass a wide range of structurally diverse new psychoactive substances (NPS), including derivatives that incorporate indole, indazole, 7-azaindole, γ-carbolinone, or carbazole heterocyclic scaffolds. The introduction of legislative measures seeking to control the availability of NPS on the recreational drug scene has likely contributed to the continued emergence of novel SCRA analogs, which often evade regulatory control. However, the detection and/or identification of azaindazole-type SCRAs in seized material has not yet been reported (September, 2021). It is plausible that SCRAs bearing a 1,3-disubstituted azaindazole scaffold may possess cannabimimetic activity, given their structural similarity with known indole, indazole, and azaindole SCRAs. In view of these antecedents, a set of four novel isomeric 4-, 5-, 6-, and 7-azaindazole analogs of the known potent indazole SCRA, MDMB-PINACA, were synthesized using a Pd-catalyzed aminocarbonylation strategy. The complementary use of ultraviolet (UV) and infrared (IR) spectroscopy, gas chromatography-mass spectrometry (GC-MS), high resolution mass spectrometry (HRMS), 1D- and 2D-nuclear magnetic resonance (NMR) spectroscopy, and high performance liquid chromatography (HPLC) has permitted the spectroscopic differentiation, unambiguous structural assignment, and rapid separation of novel isomeric 4-, 5-, 6-, and 7-azaindazole analogs of the indazole SCRA, MDMB-PINACA.

The Spicy Story of Cannabimimetic Indoles

The Sterling Research Group identified pravadoline as an aminoalkylindole (AAI) non-steroidal anti-inflammatory pain reliever. As drug design progressed, the ability of AAI analogs to block prostaglandin synthesis diminished, and antinociceptive activity was found to result from action at the CB1 cannabinoid receptor, a G-protein-coupled receptor (GPCR) abundant in the brain. Several laboratories applied computational chemistry methods to ultimately conclude that AAI and cannabinoid ligands could overlap within a common binding pocket but that WIN55212-2 primarily utilized steric interactions via aromatic stacking, whereas cannabinoid ligands required some electrostatic interactions, particularly involving the CB1 helix-3 lysine. The Huffman laboratory identified strategies to establish CB2 receptor selectivity among cannabimimetic indoles to avoid their CB1-related adverse effects, thereby stimulating preclinical studies to explore their use as anti-hyperalgesic and anti-allodynic pharmacotherapies. Some AAI analogs activate novel GPCRs referred to as "Alkyl Indole" receptors, and some AAI analogs act at the colchicine-binding site on microtubules. The AAI compounds having the greatest potency to interact with the CB1 receptor have found their way into the market as "Spice" or "K2". The sale of these alleged "herbal products" evades FDA consumer protections for proper labeling and safety as a medicine, as well as DEA scheduling as compounds having no currently accepted medical use and a high potential for abuse. The distribution to the public of potent alkyl indole synthetic cannabimimetic chemicals without regard for consumer safety contrasts with the adherence to regulatory requirements for demonstration of safety that are routinely observed by ethical pharmaceutical companies that market medicines.

The synthetic CB1 cannabinoid receptor selective agonists: Putative medical uses and their legalization

More than 500 molecules have been identified as components of Cannabis sativa (C. sativa), of which the most studied is Δ⁹-tetrahydrocannabinol (Δ⁹-THC). Several studies have suggested that Δ⁹-THC exerts diverse biological effects, ranging from fragmentation of DNA to behavioral disruptions. Currently, it is accepted that most of the pharmacological properties of Δ⁹-THC engage the activation of the cannabinoid receptors, named CB₁ and CB₂. Interestingly, multiple pieces of evidence have suggested that the cannabinoid receptors play an active role in the modulation of several diseases leading to the design of synthetic cannabinoid-like compounds. Advances in the development of synthetic CB₁ cannabinoid receptor selective agonists as therapeutical approaches are, however, limited. This review focuses on available evidence searched in PubMed regarding the synthetic CB₁ cannabinoid receptor selective agonists such as AM-1235, arachidonyl-2' chloroethylamide (ACEA), CP 50,556-1 (Levonantradol), CP-55,940, HU-210, JWH-007, JWH-018, JWH-200 (WIN 55,225), methanandamide, nabilone, O-1812, UR-144, WIN 55,212-2, nabiximols, and dronabinol. Indeed, it would be ambitious to describe all available evidence related to the synthetic CB₁ cannabinoid receptor selective agonists. However, and despite the positive evidence on the positive results of using these compounds in experimental models of health disturbances and preclinical trials, we discuss evidence in regards some concerns due to side effects.

'Synthetic cannabis': A dangerous misnomer

The term 'synthetic cannabis' has been widely used in public discourse to refer to a group of cannabinoid receptor agonists. In this paper we detail the characteristics of these drugs, and present the case that the term is a misnomer. We describe the pharmacodynamics of these drugs, their epidemiology, mechanisms of action, physiological effects and how these differ substantially from delta-9-tetrahydrocannabinol (THC). We argue that not only is the term a misnomer, but it is one with negative clinical and public health implications. Rather, the substances referred to as 'synthetic cannabis' in public discourse should instead be referred to consistently as synthetic cannabinoid receptor agonists (SCRAs), a drug class distinct from plant-derived cannabinoids. SCRAs have greater potency and efficacy, and psychostimulant-like properties. While such terminology may be used in the scientific community, it is not widely used amongst the media, general public, people who use these drugs or may potentially do so. A new terminology has the potential to reduce the confusion and harms that result from the misnomer 'synthetic cannabis'. The constant evolution of this distinct drug class necessitates a range of distinct policy responses relating to terminology, harm reduction, epidemiology, treatment, and legal status.

The use and effects of synthetic cannabinoid receptor agonists by New South Wales cannabis treatment clients

Introduction

Despite decreasing consumption by general populations, use of synthetic cannabinoid receptor agonists (SCRAs) persists in some marginalised groups, including those who use other substances. This article explores SCRA consumption in an Australian cannabis treatment sample, comparing those who report ever using SCRAs with those who have never used SCRAs.

Methods

A questionnaire orally administered in person to a convenience sample of 154 cannabis treatment service clients from New South Wales, Australia (71% male, median age 35) collected information regarding cannabis and SCRA use including motivations, effects and health-related consequences of use, demographics, other substance use and overall health. Demographic profiles and between-group differences were explored. McNemar tests compared effects of SCRA and cannabis. Logistic regression analysis determined predictors of SCRA use.

Results

Half (53%) reported lifetime SCRA use; 20% reported previous-month use. The SCRA + cannabis group displayed greater polysubstance use and psychological distress. Reduced dependence on cannabis but higher levels of other substance use may predict SCRA use. Although curiosity motivated initial SCRA consumption, perceived psychoactive strength drove continued use. SCRAs appear to induce more negative side-effects than cannabis. Of the SCRA + cannabis group, 27% sought medical assistance for SCRA use. Most (90%) preferred cannabis to SCRAs, citing superior safety, effects and consistency of cannabis.

Conclusions

Among clients seeking treatment for cannabis use, SCRA use was relatively common, although not a preferred substance. Hazardous substance use and poor mental health characterised SCRA consumers, highlighting the need for continued monitoring by researchers and treatment providers of SCRA consumption in populations who use substances.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42238-021-00091-z.

Assessment of select synthetic cannabinoid receptor agonist bias and selectivity between the type 1 and type 2 cannabinoid receptor

The first synthetic cannabinoid receptor agonists (SCRAs) were designed as tool compounds to study the endocannabinoid system's two predominant cannabinoid receptors, CB1R and CB2R. Unfortunately, novel SCRAs now represent the most rapidly proliferating novel psychoactive substances (NPS) of abuse globally. Unlike ∆9-tetrahydrocannabinol, the CB1R and CB2R partial agonist and the intoxicating constituent of Cannabis, many SCRAs characterized to date are full agonists of CB1R. Gaining additional insight into the pharmacological activity of these SCRAs is critical to assess and regulate NPSs as they enter the marketplace. The purpose of this study was to assess select SCRAs recently identified by Canadian police, border service agency, private companies and the illicit market as potential CB1R and CB2R agonists. To this end, fifteen SCRAs were screened for in vitro activity and in silico interactions at CB1R and CB2R. Several SCRAs were identified as being highly biased for cAMP inhibition or βarrestin2 recruitment and receptor subtype selectivity between CB1R and CB2R. The indazole ring and halogen-substituted butyl or pentyl moieties were identified as two structural features that may direct βarrestin2 bias. Two highly-biased SCRAs-JWH-018 2'-napthyl-N-(3-methylbutyl) isomer (biased toward cAMP inhibition) and 4-fluoro MDMB-BINACA (biased toward βarrestin2 recruitment) displayed unique and differential in vivo activity in mice. These data provide initial insight into the correlations between structure, signalling bias, and in vivo activity of the SCRAs.

Impairment of Synaptic Plasticity by Cannabis, Δ9-THC, and Synthetic Cannabinoids

The ability of neurons to dynamically and flexibly encode synaptic inputs via short- and long-term plasticity is critical to an organism's ability to learn and adapt to the environment. Whereas synaptic plasticity may be encoded by pre- or postsynaptic mechanisms, current evidence suggests that optimization of learning requires both forms of plasticity. Endogenous cannabinoids (eCBs) play critical roles in modulating synaptic transmission via activation of cannabinoid CB1 receptors (CB1Rs) in many central nervous system (CNS) regions, and the eCB system has been implicated, either directly or indirectly, in several forms of synaptic plasticity. Because of this, perturbations within the eCB signaling system can lead to impairments in a variety of learned behaviors. One agent of altered eCB signaling is exposure to "exogenous cannabinoids" such as the primary psychoactive constituent of cannabis, Δ⁹-THC, or illicit synthetic cannabinoids that in many cases have higher potency and efficacy than Δ⁹-THC. Thus, by targeting the eCB system, these agonists can produce widespread impairment of synaptic plasticity by disrupting ongoing eCB function. Here, we review studies in which Δ⁹-THC and synthetic cannabinoids impair synaptic plasticity in a variety of neuronal circuits and examine evidence that this contributes to their well-documented ability to disrupt cognition and behavior.

A transnational perspective on the evolution of the synthetic cannabinoid receptor agonists market: Comparing prison and general populations

The synthetic cannabinoid receptor agonist (SCRA) market is transnational, and the availability of individual SCRAs changes regularly in response to national and international legislative controls. This generates a cyclic pattern and near constant evolution of SCRA compounds. This study reports toxicology-based and/or seized sample-based prevalence data relating to SCRA use in prisons from Germany, the United Kingdom (UK; Scotland and Wales), and the United States (US), representing 4427 individual test results. The study examines SCRA detections in prisons from July 2018 to September 2020, and where possible, prison-based data are compared with SCRA prevalence data in the wider population. The relative influence of Chinese, other international, and national drug legislation on the prevalence of individual SCRAs in prisons is also considered. tert-Leucinate- and valinate-indole- and indazole-3-carboxamides were the most common SCRA detections, and MDMB-4en-PINACA was one of the most commonly detected SCRAs in all jurisdictions by September 2020. However, despite there being a global production and supply market, there were notable regional differences. Analog controls in German and US legislation may have led to increased compound diversity that is not reflected in the UK which has both analog controls and a blanket ban on psychoactive substances. While there were regional differences, SCRA prevalence in prisons closely aligned with the SCRAs detected on the local market, demonstrating that SCRA (and possibly other NPS) monitoring programs in prisons can act as early warning systems for the wider population in that given jurisdiction.

Detection of a New Tert-Leucinate Synthetic Cannabinoid 5F-MDMB-PICA and Its Metabolites in Human Hair: Application to Authentic Cases

Methyl 2 -[ [ 1- (5- fluoropentyl) indole - 3- carbonyl] amino] -3, 3- dimethyl - butanoate (5F-MDMB-PICA) is a new synthetic cannabinoid characterized by valinate or tert-leucinate moieties. In recent years, 5F-MDMB-PICA has been abused in the form of “spice-like” herbal incenses or electronic cigarette oil. A UHPLC-MS/MS method was developed to detect 5F-MDMB-PICA and its metabolites in human hair. Approximately 20 mg of hair was weighed and pulverized with methanol below 4°C. After ultrasonication, centrifugation and filtration, 200 μL of supernatant was placed into an autosampler vial and analyzed on a Waters Acquity UPLC HSS T₃ column (100 mm × 2.1 mm, 1.8 μm particle size) using an acetonitrile-20 mmol/L ammonium acetate (0.1% formic acid, 5% acetonitrile) gradient with a run time of 8 min. The limit of detection (LOD) ranged from 0.5 to 5 pg/mg, and the lower limit of quantitation (LLOQ) ranged from 1 to 5 pg/mg. The method was shown to be linear over a concentration range of 1–200 pg/mg. The linear correlation (R²) of the calibration curves for all analytes was >0.999. The accuracy varied from 95.4 to 107.4%, while the intra- and inter-day precision RSD values were 0.7–10.6% and 1.7–12.2%, respectively. Recoveries were within the range of 61.1–93.3%, and matrix effects were in the range of 19.1–102.6%. The validated method was successfully applied to the identification and quantification of 5F-MDMB-PICA and its metabolites in hair from authentic forensic cases.

Synthesis and in Vitro Cannabinoid Receptor 1 Activity of Recently Detected Synthetic Cannabinoids 4F-MDMB-BICA, 5F-MPP-PICA, MMB-4en-PICA, CUMYL-CBMICA, ADB-BINACA, APP-BINACA, 4F-MDMB-BINACA, MDMB-4en-PINACA, A-CHMINACA, 5F-AB-P7AICA, 5F-MDMB-P7AICA, and 5F-AP7AICA

Synthetic cannabinoid receptor agonists (SCRAs) are an evolving class of new psychoactive substances (NPS) with structurally diverse compounds emerging each year. Due to the rapid pace at which these drugs enter the market, there is often little or nil information regarding the pharmacology of these substances despite widespread human use. In this study, 12 recently emerged SCRAs (reported between 2018 and 2020) were synthesized, analytically characterized, and pharmacologically evaluated using a live cell-based nanoluciferase complementation reporter assay that monitors in vitro cannabinoid receptor type 1 (CB1) activation via its interaction with β-arrestin 2 (βarr2). All synthesized SCRAs acted as agonists of CB1, although differences in potency (EC₅₀ = 2.33-5475 nM) and efficacy (E_max = 37-378%) were noted, and several structure-activity relationships were identified. SCRAs featuring indazole cores (EC₅₀ = 2.33-159 nM) were generally of equal or greater potency than indole analogues (EC₅₀ = 32.9-330 nM) or 7-azaindole derivatives (EC₅₀ = 64.0-5475 nM). Interestingly, with the exception of APP-BINACA (E_max = 75.7%) and 5F-A-P7AICA (E_max = 37.4%), all SCRAs showed greater efficacy than the historical SCRA JWH-018 to which responses were normalized (E_max = 142-378%). The most potent CB1 agonists in the study were ADB-BINACA (EC₅₀ = 6.36 nM), 4F-MDMB-BINACA (EC₅₀ = 7.39 nM), and MDMB-4en-PINACA (EC₅₀ = 2.33 nM). Notably, all of these SCRAs featured an indazole core as well as a "bulky" tert-butyl moiety in the pendant amino acid side chain. This study confirms that recently detected SCRAs 4F-MDMB-BICA, 5F-MPP-PICA, MMB-4en-PICA, CUMYL-CBMICA, ADB-BINACA, APP-BINACA, 4F-MDMB-BINACA, MDMB-4en-PINACA, A-CHMINACA, 5F-AB-P7AICA, 5F-MDMB-P7AICA, and 5F-AP7AICA were all able to activate the CB1 receptor in vitro, albeit to different extents, and are potentially psychoactive in vivo. These results indicate that further evaluation of these widely used NPS is warranted to better understand the risks associated with human consumption of these drugs.

Biased agonism at the cannabinoid receptors - Evidence from synthetic cannabinoid receptor agonists

The type 1 and type 2 cannabinoid receptors are G protein-coupled receptors implicated in a variety of physiological processes and diseases. Synthetic cannabinoid receptor agonists (SCRAs) were originally developed to explore the therapeutic benefits of cannabinoid receptor activation, although more recently, these compounds have been diverted to the recreational drug market and are increasingly associated with incidences of toxicity. A prominent concept in contemporary pharmacology is functional selectivity or biased agonism, which describes the ability of ligands to elicit differential activation of signalling pathways through stabilisation of distinct receptor conformations. Biased agonists may maximise drug effectiveness by reducing on-target adverse effects if they are mediated by signalling pathways distinct from those that drive the therapeutic effects. For the cannabinoid receptors, it remains unclear as to which signalling pathways mediate desirable and adverse effects. However, given their structural diversity and potential to induce a plethora of signalling effects, SCRAs provide the most promising prospect for detecting and studying bias at the cannabinoid receptors. This review summarises the emerging evidence of SCRA bias at the cannabinoid receptors.

Exploring Stereochemical and Conformational Requirements at Cannabinoid Receptors for Synthetic Cannabinoids Related to SDB-006, 5F-SDB-006, CUMYL-PICA, and 5F-CUMYL-PICA

Synthetic cannabinoid receptor agonists (SCRAs) represent the most rapidly expanding class of new psychoactive substances (NPSs). Despite the prevalence and potency of recent chiral indole-3-carboxamide SCRAs, few pharmacological data are available regarding the enantiomeric bias of these NPSs toward human CB1 and CB2 receptors. A series of homochiral indole-3-carboxamides derived from (S)- and (R)-α-methylbenzylamine and featuring variation of the 1-alkyl substituent were prepared, pharmacologically evaluated, and compared to related achiral congeners derived from cumyl- and benzylamine. Competitive binding assays demonstrated that all analogues derived from either enantiomer of α-methylbenzylamine (14-17) showed affinities for CB1 (K_i = 47.9-813 nM) and CB2 (K_i = 47.9-347 nM) that were intermediate to that of the corresponding benzylic (10-13, CB1 K_i = 550 nM to >10 μM; CB2 K_i = 61.7 nM to >10 μM) and cumyl derivatives (6-9, CB1 K_i = 12.6-21.4 nM; CB2 K_i = 2.95-24.5 nM). In a fluorometric membrane potential assay, all α-methylbenzyl analogues (excluding 17) were potent, efficacious agonists of CB1 (EC₅₀ = 32-464 nM; E_max = 89-104%) and low efficacy agonists of CB2 (EC₅₀ = 54-500 nM; E_max = 52-77%), with comparable or greater potency than the benzyl analogues and much lower potency than the cumyl derivatives, consistent with binding trends. The relatively greater affinity and potency of (S)-14-17 compared to (R)-14-17 analogues at CB1 highlighted an enantiomeric bias for this series of SCRAs. Molecular dynamics simulations provided a conformational basis for the observed differences in agonist potency at CB1 pending benzylic substitution.

Synthetic cannabinoid receptor agonists: Analytical profiles and development of QMPSB, QMMSB, QMPCB, 2F-QMPSB, QMiPSB, and SGT-233

A diverse assortment of molecules designed to explore the cannabinoid receptor system and considered new psychoactive substances (NPS) have become known as synthetic cannabinoid receptor agonists (SCRAs). One group of SCRAs that has received little attention involves those exhibiting sulfamoyl benzoate, sulfamoyl benzamide, and N-benzoylpiperidine based structures. In this study, quinolin-8-yl 4-methyl-3-(piperidine-1-sulfonyl)benzoate (QMPSB), quinolin-8-yl 4-methyl-3-(morpholine-4-sulfonyl)benzoate (QMMSB), quinolin-8-yl 4-methyl-3-(piperidine-1-carbonyl)benzoate (QMPCB, SGT-11), quinolin-8-yl 3-(4,4-difluoropiperidine-1-sulfonyl)-4-methylbenzoate (2F-QMPSB, QMDFPSB, SGT-13), quinolin-8-yl 4-methyl-3-[(propan-2-yl)sulfamoyl]benzoate (QMiPSB, SGT-46), and 3-(4,4-difluoropiperidine-1-sulfonyl)-4-methyl-N-(2-phenylpropan-2-yl)benzamide (SGT-233) were extensively characterized (including data on impurities). The analytical profiles may be useful to researchers and scientists who deal with the emergence of NPS during forensic and clinical investigations. The detection of QMPSB was first published in 2016 but it is worth noting that Stargate International, a company originally formed to develop harm reduction solutions, were involved in the investigation and development of these six compounds for potential release between 2011 and early 2014. Whilst information on the prevalence of use of these particular compounds at the present time is limited, one of the key outcomes of the research performed by Stargate International reviewed here was to set the stage for the quinolin-8-yl ester head group that ultimately led to hybridization with an N-alkyl-1H-indole core to give SGT-21 and SGT-32, which became later known as PB-22 (QMPSB/JWH-018 hybrid) and BB-22, respectively, thus, opening the door to a range of SCRAs carrying the quinolin-8-yl head group from about 2012 onwards.

Assessment of synthetic cannabinoid FUB-AMB and its ester hydrolysis metabolite in human liver microsomes and human blood samples using UHPLC-MS/MS

FUB-AMB, an indazole carboxamide synthetic cannabinoid recreational drug, was one of the compounds most frequently reported to governmental agencies worldwide between 2016 and 2019. It has been implicated in intoxications and fatalities, posing a risk to public health. In the current study, FUB-AMB was incubated with human liver microsomes (HLM) to assess its metabolic fate and stability and to determine if its major ester hydrolysis metabolite (M1) was present in 12 authentic forensic human blood samples from driving under the influence of drug cases and postmortem investigations using UHPLC-MS/MS. FUB-AMB was rapidly metabolized in HLM, generating M1 that was stable through a 120-min incubation period, a finding that indicates a potential long detection window in human biological samples. M1 was identified in all blood samples, and no parent drug was detected. The authors propose that M1 is a reliable marker for inclusion in laboratory blood screens for FUB-AMB; this metabolite may be pharmacologically active like its precursor FUB-AMB. M1 frequently appears in samples in which the parent drug is undetectable and can point to the causative agent. The results suggest that it is imperative that synthetic cannabinoid laboratory assay panels include metabolites, especially known or potential pharmacologically active metabolites, particularly for compounds with short half-lives.

Cannabinoids-Promising Antimicrobial Drugs orIntoxicants with Benefits?

Novel antimicrobial drugs are urgently needed to counteract the increasing occurrence ofbacterial resistance. Extracts of Cannabis sativa have been used for the treatment of several diseasessince ancient times. However, its phytocannabinoid constituents are predominantly associated withpsychotropic effects and medical applications far beyond the treatment of infections. It has beendemonstrated that several cannabinoids show potent antimicrobial activity against primarily Grampositivebacteria including methicillin-resistant Staphylococcus aureus (MRSA). As first in vivoefficacy has been demonstrated recently, it is time to discuss whether cannabinoids are promisingantimicrobial drug candidates or overhyped intoxicants with benefits.

Designer drugs: a medicinal chemistry perspective (II)

During 2012-2018, the clandestine manufacture of new psychoactive substances (NPS) designed to circumvent substance control regulations increased exponentially worldwide, with concomitant increase in fatalities. This review focuses on three compound classes identified as synthetic opioids, synthetic amphetamines, and synthetic cannabinoids and highlights the medicinal chemistry precedents utilized by clandestine laboratories to develop new NPS with increased brain penetration, longer duration of action, and greater potency. Chemical approaches to illicit drug abuse treatment options, particularly for opioid use disorder, are also discussed.

Signalling profiles of a structurally diverse panel of synthetic cannabinoid receptor agonists

Synthetic cannabinoid receptor agonists (SCRAs) represent the most rapidly proliferating class of "designer drugs" or "new psychoactive substances". SCRAs offer unregulated alternatives to cannabis that evade routine drug tests, but their use is increasingly associated with severe toxicity and death worldwide. Little is currently known about SCRA molecular pharmacology, or the mechanisms underpinning their toxicity, although the effects are believed to be primarily mediated by the type 1 cannabinoid receptor (CB₁). In this study, we aimed to characterise the signalling profiles of a structurally diverse panel of novel SCRAs at CB₁. We compare SCRAs to traditional reference cannabinoids CP55,940, WIN55,212-2, and THC. The activity of the SCRAs was assessed in key receptor signalling and regulatory pathways, including cAMP production, translocation of β-arrestin 1 and 2, and receptor internalisation. The activity profiles of the ligands were also evaluated using operational analysis to identify ligand bias. Results revealed that SCRAs activities were relatively balanced in the pathways evaluated (compared to WIN55,212-2), although 5F-CUMYL-P7AICA and XLR-11 possessed partial efficacy in cAMP stimulation and β-arrestin translocation. Notably, the SCRAs showed distinct potency and efficacy profiles compared to THC. In particular, while the majority of SCRAs demonstrated robust β-arrestin translocation, cAMP stimulation, and internalisation, THC failed to elicit high efficacy responses in any of these assays. Further study is required to delineate if these pathways could contribute to SCRA toxicity in humans.

Different receptor mechanisms underlying phytocannabinoid- versus synthetic cannabinoid-induced tetrad effects: Opposite roles of CB1 /CB2 versus GPR55 receptors

BACKGROUND AND PURPOSE

Cannabis or cannabinoids produce characteristic tetrad effects-analgesia, hypothermia, catalepsy and suppressed locomotion, which are believed to be mediated by the activation of cannabinoid CB₁ receptors. Given recent findings of CB₂ and GPR55 receptors in the brain, we examined whether these receptors are also involved in cannabinoid action.

EXPERIMENTAL APPROACH

We compared Δ⁹ -tetrahydrocannabinol (Δ⁹ -THC)-, WIN55212-2-, or XLR11-induced tetrad effects between wild-type (WT) and each genotype of CB₁ -, CB₂ - or GPR55-knockout (KO) mice and then observed the effects of antagonists of these receptors on these tetrad effects in WT mice.

KEY RESULTS

Systemic administration of Δ⁹ -THC, WIN55212-2 or XLR11 produced dose-dependent tetrad effects in WT mice. Genetic deletion or pharmacological blockade of CB₁ receptors abolished the tetrad effects produced by all three cannabinoids. Unexpectedly, genetic deletion of CB₂ receptor abolished analgesia and catalepsy produced by Δ⁹ -THC or WIN55212-2, but not by XLR11. Microinjections of Δ⁹ -THC into the lateral ventricles also produced tetrad effects in WT, but not in CB₁ -KO mice. CB₂ -KO mice displayed a reduction in intraventricular Δ⁹ -THC-induced analgesia and catalepsy. In contrast to CB₁ and CB₂ receptors, genetic deletion of GPR55 receptors caused enhanced responses to Δ⁹ -THC or WIN55212-2. Antagonisim of CB₁ , CB₂ or GPR55 receptors produced alterations similar to those observed in each genotype mouse line.

CONCLUSIONS AND IMPLICATIONS

These findings suggest that in addition to CB₁ , both CB₂ and GPR55 receptors are also involved in some pharmacological effects produced by cannabinoids. CB₁ /CB₂ , in contrast to GPR55, receptors appears to play opposite roles in cannabinoid action.

Filter Cone Spray Ionization Coupled to a Portable MS System: Application to On-Site Forensic Evidence and Environmental Sample Analysis

The complexity of field-borne sample matrices and the instrumental constraints of portable mass spectrometers (MS) often necessitate that preparative steps are added prior to ambient MS methods when operated on-site, but the corresponding decrease in throughput and experimental simplicity can make field operation impractical. To this end, we report a modified ambient MS method, filter cone spray ionization (FCSI), specifically designed for simple, yet robust, processing of bulk forensic evidence and environmental samples using a fieldable MS system. This paper-crafted source utilizes low-cost laboratory consumables to produce a conical structure that serves as a disposable, spray-based ionization source. Integrated extraction and filtration capabilities mitigate sample heterogeneity and carryover concerns and expedite sample processing, as characterized through the analysis of a variety of authentic forensic evidence types (e.g., abused pharma tablets, counterfeit/adulterated tablets, crystal-based drugs, synthetic marijuana, toxicological specimens) and contaminated soil samples. The data presented herein suggests that the FCSI-MS design could prove robust to the rigors of field-borne, bulk sample screening, overcoming the inefficiencies of other ambient MS methods for these sample classes. Novel applications of FCSI-MS are also examined, such as the coupling to trace evidence vacuum filtration media.