Activity-based detection of consumption of synthetic cannabinoids in authentic urine samples using a stable cannabinoid reporter system

Synthetic cannabinoids (SCs) continue to be the largest group of new psychoactive substances (NPS) monitored by the European Monitoring Center of Drugs and Drugs of Abuse (EMCDDA). The identification and subsequent prohibition of single SCs has driven clandestine chemists to produce analogues of increasing structural diversity, intended to evade legislation. That structural diversity, combined with the mostly unknown metabolic profiles of these new SCs, poses a big challenge for the conventional targeted analytical assays, as it is difficult to screen for "unknown" compounds. Therefore, an alternative screening method, not directly based on the structure but on the activity of the SC, may offer a solution for this problem. We generated stable CB1 and CB2 receptor activation assays based on functional complementation of a split NanoLuc luciferase and used these to test an expanded set of recent SCs (UR-144, XLR-11, and their thermal degradation products; AB-CHMINACA and ADB-CHMINACA) and their major phase I metabolites. By doing so, we demonstrate that several major metabolites of these SCs retain their activity at the cannabinoid receptors. These active metabolites may prolong the parent compound's psychotropic and physiological effects and may contribute to the toxicity profile. Utility of the generated stable cell systems as a first -line screening tool for SCs in urine was also demonstrated using a relatively large set of authentic urine samples. Our data indicate that the stable CB reporter assays detect CB receptor, activation by extracts of urine in which SCs (or their metabolites) are present at low- or subnanomolar (ng/mL) level. Hence, the developed assays do not only allow activity profiling of SCs and their metabolites, it may also serve as a screening tool, complementing targeted and untargeted analytical assays and preceding analytical (mass spectrometry based) confirmation

In vitro functional characterization of a panel of non-fentanyl opioid new psychoactive substances

The landscape of new psychoactive substances (NPS) is constantly evolving, with new compounds entering the illicit drug market at a continuous pace. Of these, opioid NPS form a threat given their high potency and prevalence. Whereas previously, the use of fentanyl and fentanyl derivatives was the main point of attention, legislations have reacted accordingly, whichmay have been a driving force towards the (ab)use of alternative µ-opioid receptor (MOR) agonists. In contrast to fentanyl (analogues), details on these novel non-fentanyl opioid NPS are scarce. We investigated the biological activity of a panel of 11 ‘alternative’, newly emerging MOR agonists (2-methyl-AP-237, AP-237, bromadol, brorphine, butorphanol, isotonitazene, mitragynine, 7-OH-mitragynine, MT-45, piperidylthiambutene, and tianeptine) using two closely related in vitro MOR activation bio-assays, monitoring either G protein (mini-Gi), or β-arrestin2 (βarr2) recruitment. Activity profles were obtained for all tested compounds, with values for potency (EC50) ranging from 1.89 nM (bromadol) to>3 µM (AP-237 and tianeptine). Bromadol, brorphine, isotonitazene, piperidylthiambutene, and tianeptine had the highest efcacy (Emax) values, exceeding that of the reference compound hydromorphone≥1.3-fold (βarr2 assay) and>2.6-fold (mini-Gi assay). Information on the recruitment of two distinct signaling molecules additionally enabled evaluation of biased agonism; none of the evaluated opioids being signifcantly biased. Taken together, this study is the frst to systematically investigate the in vitro biological activity of a diverse panel of emerging non-fentanyl opioid NPS at MOR. Given the known danger of (fatal) intoxications with many opioid NPS, it is important to continuously monitor and characterize newly emerging compounds

In vitro structure-activity relationship determination of 30 psychedelic new psychoactive substances by means of beta-arrestin 2 recruitment to the serotonin 2A receptor

Serotonergic psychedelics, substances exerting their efects primarily through the serotonin 2A receptor (5-HT2AR), continue to comprise a substantial portion of reported new psychoactive substances (NPS). The exact mechanisms of action of psychedelics still remain to be elucidated further, and certain pathways remain largely unexplored on a molecular level for this group of compounds. A systematic comparison of substances belonging to diferent subclasses, monitoring the receptor-proximal β-arrestin 2 recruitment, is lacking. Based on a previously reported in vitro bioassay employing functional complementation of a split nanoluciferase to monitor β-arrestin 2 recruitment to the 5-HT2AR, we here report on the setup of a stable HEK 293 T cell-based bioassay. Following verifcation of the performance of this new stable cell system as compared to a system based on transient transfection, the stable expression system was deemed suitable for the pharmacological characterization of psychedelic NPS. Subsequently, it was applied for the in vitro assessment of the structure–activity relationship of a set of 30 substances, representing diferent subclasses of phenylalkylamine psychedelics, among which 12 phenethylamine derivatives (2C-X), 7 phenylisopropylamines (DOx) and 11 N-benzylderivatives (25X-NB). The resulting potency and efcacy values provide insights into the structure–activity relationship of the tested compounds, overall confrm fndings observed with other reported in vitro assays, and even show a signifcant correlation with estimated common doses. This approach, in which a large series of psychedelic NPS belonging to diferent subclasses is comparatively tested, using a same assay setup, monitoring a receptor-proximal event, not only gives pharmacological insights, but may also allow prioritization of legal actions related to the most potent -and potentially dangerous- compounds

Semiquantitative activity-based detection of JWH-018, a synthetic cannabinoid receptor agonist, in oral fluid after vaping

The rapid proliferation of new synthetic cannabinoid receptor agonists (SCRAs) has initiated considerable interest in the development of so-called “untargeted” screening strategies. One of these new screening technologies involves the activity-based detection of SCRAs. In this study, we evaluated whether (synthetic) cannabinoid activity can be detected in oral fluid (OF) and, if so, whether it correlates with SCRA concentrations. OF was collected at several time points in a placebo-controlled JWH-018 administration study. The outcome of the cell-based cannabinoid reporter system, which monitored the cannabinoid receptor activation, was compared to the quantitative data for JWH-018, obtained via a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. A total of 175 OF samples were collected and analyzed via both methods. The cannabinoid reporter assay correctly classified the vast majority of the samples as either negative (<0.25 ng/mL; 74/75 = 99%) or having low (0.25−1.5 ng/mL; 16/16 = 100% and 1.5−10 ng/mL; 37/41 = 90%), mid (10−100 ng/mL; 23/25 = 92%) or high (>100 ng/mL; 16/18 = 89%) JWH-018 concentrations. Passing−Bablok regression analysis yielded a good linear correlation, with no proportional difference between both methods (slope 0.97; 95% confidence interval 0.86−1.14) and only a small systematic difference. This is the first study to demonstrate the applicability of an untargeted, activity-based approach for SCRA detection in OF. Additionally, the outcome of the cannabinoid reporter assay was compared to the gold standard (LC-MS/MS), showing a good correlation between both methods, indicating that the cannabinoid reporter assay can be used for an estimation of drug concentrations

In vitro activity profiling of Cumyl-PEGACLONE variants at the CB1 receptor : fluorination versus isomer exploration

Synthetic cannabinoid receptor agonists (SCRAs) are one of the largest groups of new psychoactive substances monitored in Europe. SCRAs are known to typically exert higher cannabinoid activity than tetrahydrocannabinol from cannabis, thereby entailing a greater health risk. Both Cumyl-PEGACLONE and 5F-Cumyl-PEGACLONE were not controlled by the national legislation upon their first detection in Germany in 2016 and 2017, respectively, and have been linked to several fatalities. In this study, the CB1 receptor activity of these compounds, together with two newly synthesized structural isomers (Cumyl-PEGACLONE ethylbenzyl isomer and npropylphenyl isomer), was assessed using two different in vitro receptor-proximal bioassays, monitoring the recruitment of either β-arrestin2 (β-arr2) or a modified G protein (mini-Gαi) to the activated CB1 receptor. In terms of both potency and relative efficacy, Cumyl-PEGACLONE and 5F-Cumyl-PEGACLONE were found to exert strong CB1 activation, with sub-nanomolar EC50 values and efficacy values exceeding those of the reference agonist JWH-018 threefold (β-arr2 assay) or almost twofold (mini-Gαi assay). The ethylbenzyl and n-propylphenyl isomers exhibited a strongly reduced CB1 activity (EC50 values >100 nM; efficacy <40% relative to JWH-018), which is hypothesized to originate from steric hindrance in the ligand-binding pocket. None of the evaluated compounds exhibited significant biased agonism. In conclusion, the functional assays applied here allowed us to demonstrate that 5-fluorination of Cumyl-PEGACLONE is not linked to an intrinsically higher CB1 activation potential and that the ethylbenzyl and n-propylphenyl isomers yield a strongly reduced CB1 activation

Are the N-demethylated metabolites of U-47700 more active than their parent compound? In vitro μ-opioid receptor activation of N-desmethyl-U-47700 and N,N-bisdesmethyl-U-47700

Studies on the tissue distribution of the new synthetic opioid U-47700 and its main metabolite N-desmethyl-U-47700 revealed about sixfold higher metabolite concentrations in pig brain as compared with the parent compound. To better assess the toxic potential of this drug, the aim of this study was to assess the in vitro μ-opioid receptor (MOR) activation potential of the main metabolites of U-47700, Ndesmethyl-U-47700, and N,N-bisdesmethyl-U-47700, using a live cell-based reporter assay based on NanoLuc Binary Technology®. Cells stably expressing human MOR and β-arrestin 2 (βarr2), each fused via a flexible linker to two complementary inactive subunits of the nanoluciferase, were seeded on poly-D-lysine-coated 96-well plates and treated with N-desmethyl-U-47700, N,N-bisdesmethyl-U-47700, U-47700, or hydromorphone as reference standard. MOR activation results in functional complementation of the nanoluciferase, which can be assessed via luminescence monitoring. The potency of the metabolites is lower than that of U-47700 (EC50 of 186 nM for U-47700, 3770 nM for N-desmethyl-U-47700, and >5 μM for N,N-bisdesmethylU-47700). The maximal efficacy (Emax) observed (relative to hydromorphone, set arbitrarily at 100%) decreased from 183% to 127% and 39.2% for U-47700, N-desmethyl-U-47700, and N,N-bisdesmethyl-U-47700, respectively. Thus, the loss of one or two methyl groups reduced the MOR activation potential, which was more pronounced if both methyl groups were removed. It is thus anticipated that the impact on MOR exerted by the higher metabolite concentration in brain has only little—if any relevance for the strong toxic effects of U-47700

Detection and activity profiling of synthetic cannabinoids and their metabolites with a newly developed bioassay

Synthetic cannabinoids (SCs) are the largest group of compounds currently monitored in Europe by the EU Early Warning System on new psychoactive substances. Emerging recreational use of these products has led to multiple cases of adverse health effects and even death. In contrast to marijuana, where Delta(9)-tetrahydrocannabinol (Delta(THC)-T-9) is metabolized to only one major active metabolite, it has been reported that several major phase I metabolites of SCs remain biologically active, exerting cannabinoid (CB) receptor affinity, potency, and efficacy greater than those of Delta(THC)-T-9. It is therefore reasonable that more SCs can also be biotransformed into molecules with various levels of CB activity. Here, we developed and applied a new G-protein coupled receptor (GPCR) activation assay based on NanoLuc binary technology (Promega). More specifically, by demonstrating CB1 and CB2 receptor activation by JWH-018 and a selection of its metabolites, we are the first to show the suitability of the newly developed bioassay for monitoring GPCR-mediated activity. We also successfully applied this reporter system to evaluate the in vitro activity of JWH-122, JWH-210, and PB-22, their S-fluoro analogues (MAM-2201, EAM-2201, and SF-PB-22, respectively), and their main phase I metabolites. By doing so, we demonstrate that several major metabolites of these SCs retain their activity at cannabinoid receptors. All of these active metabolites may prolong the parent compound's psychotropic and physiological effects and may contribute to its toxicity profile. We also demonstrate a proof of concept of the applicability of the newly developed bioassay for screening urine for CB receptor activity exerted by SCs

First report on brorphine : the next opioid on the deadly new psychoactive substance horizon?

New psychoactive substances (NPS) continue to appear on the drug market. Until recently, new synthetic opioids, which are amongst the most dangerous NPS, primarily encompassed analogues of the potent analgesic fentanyl. Lately, also other new synthetic opioids have increasingly started to surface. This is the first report on the identification and full chemical characterization of brorphine, a novel potent synthetic opioid with a piperidine benzimidazolone structure. Brorphine was identified in a powder and in the serum of a patient seeking medical help for detoxification. Liquid chromatography–high resolution mass spectrometry (LC–HRMS) identified an exact mass of m/z 400.1020 and 402.1005 for the compound, corresponding to both bromine isotopes. Further chemical characterization was performed by gas chromatography–mass spectrometry (GC–MS), LC–diode array detection (DAD) and Fourier-transform infrared (FT-IR) spectroscopy analyses. Finally, the structure was confirmed by performing 1H- and 13C-NMR spectroscopy. In vitro biological activity of brorphine was determined by a cell-based µ-opioid receptor (MOR) activation assay, resulting in an EC50 of 30.9 nM (13.5 ng/mL) and an Emax of 209% relative to hydromorphone, confirming the high potency and efficacy of this compound. In a serum sample of the patient, brorphine and a hydroxy-metabolite were found using the LC–HRMS screening method. The presence of opioid activity in the serum was also confirmed via the activity-based opioid screening assay. The occurrence of brorphine is yet another example of how the illicit drug market is continuously evolving in an attempt to escape international legislation. Its high potency poses a serious and imminent health threat for any user

Shape Matters: The Application of Activity‐Based In Vitro Bioassays and Chiral Profiling to the Pharmacological Evaluation of Synthetic Cannabinoid Receptor Agonists in Drug‐Infused Papers Seized in Prisons

Synthetic cannabinoid receptor agonists (SCRAs) elicit many of their psychoactive effects via type‐1 human cannabinoid (CB1) receptors. Enantiomer pairs of eight tert‐leucinate or valinate indole‐ and indazole‐3‐carboxamide SCRAs were synthesized and their CB1 potency and efficacy assessed using an in vitro β‐arrestin recruitment assay in a HEK239T stable cell system. A chiral high‐performance liquid chromatography method with photodiode array and/or quadrupole‐time of flight mass spectrometry detection (HPLC‐PDA and HPLC‐PDA‐QToF‐MS) was applied to 177 SCRA infused paper samples seized in Scottish prisons between 2018 and 2020. In most samples, SCRAs were almost enantiopure (S)‐enantiomer (>98% of total chromatographic peak area), although in some (n=18), 2 to 16% of the (R)‐enantiomer was detected. (S)‐enantiomers are consistently more potent than (R)‐enantiomers and often more efficacious. The importance of SCRA‐CB1 receptor interactions in the ‘head’ or ‘linked group’ moiety is demonstrated, with the conformation of the ‘bulky’ tert‐leucinate group greatly affecting potency (by up to a factor of 374), significantly greater than the difference observed between valinate SCRA enantiomers. (S)‐MDMB‐4en‐PINACA, (S)‐4F‐MDMB‐BINACA and (S)‐5F‐MDMB‐PICA are currently the most prevalent SCRAs in Scottish prisons and all have similar high potency (EC50, 1‐5 nM) and efficacy. Infused paper samples were compared using estimated intrinsic efficacy at the CB1 receptor (EIECB1) to evaluate samples with variable SCRA content. Given their similar potency and efficacy, any variation in CB1‐receptor mediated psychoactive effects are likely to derive from variation in dose, mode of use, pharmacokinetic differences and individual factors affecting the user, rather than differences in the specific SCRA present