In Vitro Metabolite Profiling of ADB-FUBINACA, A New Synthetic Cannabinoid

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.

ADB-HEXINACA-a novel synthetic cannabinoid with a hexyl substituent: phase I metabolism in authentic urine samples, a case report and prevalence on the German market

Synthetic cannabinoid receptor agonists (SCRAs) are one of the largest groups of new psychoactive substances (NPS). Yet, another novel analog started spreading on the NPS market around 2021. Soon after, the substance could be analytically characterized in herbal material as ADB-HEXINACA, an SCRA containing a hexyl-substituted tail on the indazole core. Here, we present suitable urinary markers to prove the consumption of this analog, a case report of acute polydrug intoxication and data on its prevalence in Germany. Anticipated phase I metabolites were detected in 12 authentic urine samples that were collected for abstinence control and analyzed by ultra-performance liquid chromatography coupled to a time-of-flight mass spectrometer (UPLC-qToF-MS). The results of in vivo samples were confirmed by analysis of in vitro incubates with pooled human liver microsomes (pHLMs). Forensic samples were used to assess the prevalence of ADB-HEXINACA. Thirty-two phase I metabolites were detected in the authentic urine samples. The main metabolites resulted from amide hydrolysis in combination with either monohydroxylation or ketone formation at the hexyl moiety (M15 and M26), the monitoring of which is recommended as a proof of consumption. ADB-HEXINACA was detected in 3.5% of SCRA positive urine samples collected for abstinence control in Freiburg up to December 2022 and in 5.5% of the SCRA positive blood/serum samples. The hexyl substituent of ADB-HEXINACA allows for the detection of specific urinary biomarkers suggested as analytical targets to confirm its prior intake. ADB-HEXINACA had a rather low prevalence in Germany, alternating months of higher prevalence with periods of total absence.

Metabolic profiling of a new synthetic cannabinoid receptor agonist, ADMB-FUBIATA, with human liver microsomes, human primary hepatocytes and human recombinant CYP450 enzymes using LC-quadrupole-orbitrap MS

A novel synthetic cannabinoid receptor agonist (SCRA), ADMB-FUBIATA, featuring an acetamide-linked structure, has emerged on the illicit drug market. To provide dependable verification of its consumption and identify reliable biomarkers, we investigated an in vitro metabolism study of ADMB-FUBIATA incubated with human primary hepatocytes (HPHs) for the first time and correlated our findings with those from human liver microsomes (HLMs). In this work, ADMB-FUBIATA (10 μM) was incubated with HLM and HPH for 1 and 5 h, respectively, and then subjected to LC-quadrupole-orbitrap MS. A total of 25 metabolites across 8 metabolic pathways were identified after incubation with HLM and HPH, respectively. Monohydroxylation and N-dealkylation were the major metabolic pathways, and formation to ketone was first identified. In addition, the metabolism of ADMB-FUBIATA were found to be mediated by multiple CYP450 enzymes, predominantly CYP2C19, 2D6, and 3A4. This research also initially characterized the fragmentation patterns of the metabolites of ADMB-FUBIATA, elaborating on their structural relationship with ADMB-FUBIATA analogs. To effectively monitor ADMB-FUBIATA abuse, metabolites M4 and M1 were proposed as reliable biomarkers by cross-validating the HLM and HPH incubation results.

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.

Log D7.4 and plasma protein binding of synthetic cannabinoid receptor agonists and a comparison of experimental and predicted lipophilicity

The emergence of new synthetic cannabinoid receptor agonists (SCRAs) onto the illicit drugs market continues to cause harm, and the overall availability of physicochemical and pharmacokinetic data for new psychoactive substances is lacking. The lipophilicity of 23 SCRAs and the plasma protein binding (PPB) of 11 SCRAs was determined. Lipophilicity was determined using a validated chromatographic hydrophobicity index (CHI) log D method; tested SCRAs showed moderate to high lipophilicity, with experimental log D7.4 ranging from 2.48 (AB-FUBINACA) to 4.95 (4F-ABUTINACA). These results were also compared to in silico predictions generated using seven commercially available software packages and online tools (Canvas; ChemDraw; Gastroplus; MoKa; PreADMET; SwissADME; and XlogP). Licenced, dedicated software packages provided more accurate lipophilicity predictions than those which were free or had prediction as a secondary function; however, the latter still provided competitive estimates in most cases. PPB of tested SCRAs, as determined by equilibrium dialysis, was in the upper range of the lipophilicity scale, ranging from 90.8% (ADB-BUTINACA) to 99.9% (BZO-HEXOXIZID). The high PPB of these drugs may contribute to reduced rate of clearance and extended durations of pharmacological effects compared to lesser-bound SCRAs. The presented data improve understanding of the behaviour of these drugs in the body. Ultimately, similar data and predictions may be used in the prediction of the structure and properties of drugs yet to emerge on the illicit market.

In vitro metabolism study of ADB-P-5Br-INACA and ADB-4en-P-5Br-INACA using human hepatocytes, liver microsomes, and in-house synthesized references

Synthetic cannabinoids (SCs) remain a major public health concern, as they continuously are linked to severe intoxications and drug-related deaths worldwide. As new SCs continue to emerge on the illicit drug market, an understanding of SC metabolism is needed to identify formed metabolites that may serve as biomarkers in forensic toxicology screening and for understanding the pharmacokinetics of the drugs. In this work, the metabolism of ADB-4en-P-5Br-INACA and ADB-P-5Br-INACA ((S)-N-(1-amino-3,3-dimethyl-1-oxobutan-2-yl)-5-bromo-1-(pent-4-en-1-yl)-1H-indazole-3-carboxamide, (S)-N-(1-amino-3,3-dimethyl-1-oxobutan-2-yl)-5-bromo-1-pentyl-1H-indazole-3-carboxamide respectively) were investigated using human hepatocytes in vitro and in-house synthesized references. Both SCs were incubated with pooled human hepatocytes over 3 h, with the aim to identify unique and abundant metabolites using liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). In total nine metabolites were identified for ADB-4en-P-5Br-INACA and 10 metabolites for ADB-P-5Br-INACA. The observed biotransformations included dihydrodiol formation, terminal amide hydrolysis, hydroxylation, dehydrogenation, carbonyl formation, glucuronidation, and combinations thereof. The major metabolites were confirmed by in-house synthesized references. Recommended biomarkers for ADB-P-5Br-INACA and ADB-4en-P-5Br-INACA are the terminal hydroxy and dihydrodiol metabolite respectively.

Metabolism of ADB-FUBIATA in zebrafish and pooled human liver microsomes investigated by liquid chromatography-high-resolution mass spectrometry

RATIONALE

ADB-FUBIATA is one of the most recently identified new psychoactive substance (NPS) of synthetic cannabinoids. The co-use of in vitro (human liver microsomes) and in vivo (zebrafish) models offers abundant metabolites and may give a deep insight into the metabolism of NPS.

METHODS

In vivo and in vitro metabolic studies of new synthetic cannabinoid ADB-FUBIATA were carried out using zebrafish and pooled human liver microsome models. Metabilites were structurally characterized by liquid chromatography-high-resolution mass spectrometry.

RESULTS

In total, 18 metabolites were discovered and identified in the pooled human liver microsomes and zebrafish, including seventeen phase I metabolites and one phase II metabolite. The main metabolic pathways of ADB-FUBIATA were hydroxylation, dehydrogenation, N-dealkylation, amide hydrolysis, glucuronidation, and combination thereof.

CONCLUSION

Hydroxylated metabolites can be recommended as metabolic markers for ADB-FUBIATA because of the structural characteristics and high intensity. These metabolism characteristics of ADB-FUBIATA were useful for its further forensic or clinical related investigations.

GC-MS/MS analysis of synthetic cannabinoids 5F-MDMB-PICA and 5F-CUMYL-PICA in forensic cases

Aim: Validate a method to quantify 1-(5-fluoropentyl)-N-(2-phenylpropan-2-yl)-1H-indole-3-carboxamide (5F-CUMYL-PICA) and methyl 2-[[1-(5-fluoropentyl) indole-3-carbonyl] amino]-3,3-dimethyl-butanoate (5F-MDMB-PICA) in blood samples using GC-MS/MS. Materials & methods: A solid-phase extraction (SPE) method has been developed to quantify 5F-MDMB-PICA and 5F-CUMYL-PICA in authentic human blood samples. Results & conclusion: The limit of detection (LOD) was 0.1 and 0.11 ng/ml for 5F-CUMYL-PICA and 5F-MDMB-PICA, respectively, while the limit of quantification (LOQ) was 0.50 ng/ml for both two compounds. Recovery was 91.40, 82.54 and 85.10% for SPE, supported liquid extraction (SLE) and ISOLUTE C18; matrix effects 15, 24 and 22.5% for SPE, SLE and ISOLUTE C18; accuracy was 2.4-5.5 and 3.9-7.3% for SPE, SLE and ISOLUTE C18, while precision was 4.6-7.7 and 6.4-8.3% for SPE, SLE and ISOLUTE C18, respectively. The concentrations of 5F-CUMYL-PICA and 5F-MDMB-PICA in the authentic human blood samples were 2.18 and 3.07 ng/ml, respectively. The validated method was successfully used in supporting the quantification of analytes in blood.

Indazole-derived synthetic cannabinoids: Absolute configuration determination and structure characterization by circular dichroism and DFT calculations

An increasing number of products containing synthetic cannabinoids pose a growing crisis to public health worldwide. Recently, a rising number of cases of serious adverse health effects, intoxications, and death cases associated with synthetic cannabinoids were reported. The current study represents the comprehensive structural analysis of three new synthetic cannabinoids (AB-, ADB- and AMB-FUBINACA) in solution investigated by electronic and vibrational circular dichroism together with the conventional methods of infrared and ultraviolet absorption spectroscopy, all supported by the density functional theory (DFT) calculations. The best level of theory to reproduce the experimental wavenumbers and wavelengths was found to be the B3PW91 method with a 6-311++G(d,p) basis set including the implicit solvent effect simulation. Very good agreement between the experimental and simulated spectra allowed us to determine the absolute configuration and a detailed interpretation of the IR absorption, VCD, ECD and UV spectra of AB-, ADB- and AMB-FUBINACA. In addition, the HOMO and LUMO electronic transitions were calculated.

Fourth Generation of Synthetic Cannabinoid Receptor Agonists: A Review on the Latest Insights

BACKGROUND

Over the past few years, an emerging number of new psychoactive substances (NPSs) entered the illicit market. NPSs are designed to resemble the effects of classical drugs of abuse, reinforcing their effects and duration. Among the most abused NPS, synthetic cannabinoids are cannabinoid receptor agonists (SCRAs) that mimic the effect of the main psychotropic phytocannabinoid Δ9-tetrahydrocannabinol (THC).

METHODS

We herein reviewed the international literature to provide available information on the newest SCRAs generation.

RESULTS

Compared to the previous SCRAs generations, the structures of the last generation result in increased affinity for and efficacy at cannabinoid CB₁ receptors, which are thought to be mainly responsible for the psychoactive effects of THC and its analogues. Accordingly, these more potent cannabimimetic effects may increase the number of adverse reactions such as neurological disorders (e.g., psychosis, agitation, irritability, paranoia, confusion, and anxiety), psychiatric episodes (e.g., hallucinations, delusions, self-harm), other physical conditions (e.g., tachycardia, hypertension, arrhythmia, chest pain, nausea, vomiting, and fever) and deaths. In the last decade, more than a hundred SCRAs from different chemical classes emerged on the illicit web market. SCRAs have been thoroughly studied: they were physico-chemically characterized, and pharmaco-toxicological characteristics were investigated. The last SCRAs generations include increasingly potent and toxic compounds, posing a potential health threat to consumers.

CONCLUSION

From November 2017 to February 2021, at least 20 new "fourth-generation" SCRAs were formally reported to international drug agencies. Our understanding of the neurotoxicity of these compounds is still limited due to the lack of global data, but their potency and their toxicity are likely higher than those of the previous generations.

Metabolic profiles and screening tactics for MDMB-4en-PINACA in human urine and serum samples

MDMB-4en-PINACA (Methyl 3,3-dimethyl-2-[1-(pent-4-en-1-yl)-1H-indazole-3-carboxamido] butanoate) is a potent agonist of the CB1 receptor. In 2021, it was one of the most common synthetic cannabinoid receptor agonists (SCRAs) seized by the Beijing Drug Control Agency. MDMB-4en-PINACA can be hard to detect in biological specimens because of ester hydrolysis. In this work, a highly sensitive liquid chromatography-high-resolution mass spectrometry (LC-HRMS) method was developed for the detection of MDMB-4en-PINACA metabolites in urine, serum, and hair samples. Metabolites from authentic samples were compared with those from human liver microsomes (HLMs) in vitro and in zebrafish in vivo. A total of 75 metabolites, including 44 previously unreported metabolites, were identified from urine samples. We found that 11 metabolic pathways were involved in MDMB-4en-PINACA metabolism, including acetylation, a novel metabolic pathway for SCRAs. Our results revealed that ester hydrolysis and hydroxylation were to the major metabolic pathways involved in MDMB-4en-PINACA metabolism. Using serum samples, we detected 9 metabolites along with the parent drug. Only the parent drug was detected using hair samples. The existence of ADB-4en-PINACA makes the currently used biomarkers for MDMB-4enPINACA not very specific for the intake of MDMB-4en-PINACA. Therefore, based on the identified metabolites and their structural features, we propose more sensitive screening tactics for MDMB-4en-PINACA using urine and serum samples.

In-depth comparison of the metabolic and pharmacokinetic behaviour of the structurally related synthetic cannabinoids AMB-FUBINACA and AMB-CHMICA in rats

Synthetic cannabinoids receptor agonists (SCRAs) are often almost completely metabolised, and hence their pharmacokinetics should be carefully evaluated for determining the most adequate biomarker in toxicological analysis. Two structurally related SCRAs, AMB-FUBINACA and AMB-CHMICA, were selected to evaluate their in vivo metabolism and pharmacokinetics using male Sprague-Dawley rats. Brain, liver, kidney, blood (serum) and urine samples were collected at different times to assess the differences in metabolism, metabolic reactions, tissue distribution and excretion. Both compounds experimented O-demethyl reaction, which occurred more rapidly for AMB-FUBINACA. The parent compounds and O-demethyl metabolites were highly bioaccumulated in liver, and were still detected in this tissue 48 h after injection. The different indazole/indole N-functionalisation produced diverse metabolic reactions in this moiety and thus, different urinary metabolites were formed. Out of the two compounds, AMB-FUBINACA seemed to easily cross the blood-brain barrier, presenting higher brain/serum concentrations ratio than AMB-CHMICA.

Synthetic cannabinoids are amongst the most widely used psychoactive drugs which are tightly controlled by government agencies around the world. Here, pharmacokinetics of two synthetic cannabinoids in rats are evaluated along with their metabolites and tissue distribution, aiding in identifying distinct biomarkers that reflect the consumption of synthetic cannabinoids based on the tissue.

Pharmacokinetics, plasma protein binding, and metabolism of a potential natural chemosensitizer from Marsdenia tenacissima in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Marsdenia tenacissima (Roxb.) Wight et Arn is a medicinal plant mainly distributed in southwest China. It is used in folk medicine for the treatment of tumors and is synergistic with chemotherapies. In our previous study, 11α-O-2-methybutyryl-12β-O-tigloyl-tenacigenin B (MT2), a main steroid aglycone isolated from the total aglycones of M. tenacissima, significantly enhanced the in vivo antitumor effect of paclitaxel in mice bearing human tumor xenografts, showing its potential as a chemosensitizer. However, the pharmacokinetic characteristics, plasma protein binding rate, and metabolic profile of MT2 remain unclear.

AIM OF THE STUDY

To elucidate the pharmacokinetic characteristics, plasma protein binding rate, and metabolic profile of MT2 in rats.

MATERIALS AND METHODS

MT2 in rat plasma and phosphate-buffered saline was quantified using ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method, while the MT2 metabolites in rat liver microsomes were analyzed using UPLC-triple time-of-flight MS/MS.

RESULTS

For intravenously administered MT2, the maximum plasma concentration and the area under the plasma concentration-time curve indicated dose dependency, while the elimination half-life time, the mean residence time, apparent volume of distribution and total apparent clearance values remained relatively unchanged in both the 5 mg/kg and 10 mg/kg groups. For orally administered MT2, the bioavailability was 1.08-1.11%. In rat plasma, MT2 exhibited a protein binding rate of 93.84-94.96%. In rat liver microsomes, MT2 was metabolized by oxidation alone or in combination with demethylation, and five MT2 metabolites were identified.

CONCLUSION

MT2 has low oral bioavailability and a high plasma protein binding rate in rats. After administration, MT2 is transformed into oxidative metabolites in the liver. To achieve a high blood concentration of MT2, it should be administered intravenously. These findings would serve as a reference for further MT2-based pharmacological study and drug development.

In silico prediction, LC-HRMS/MS analysis, and targeted/untargeted data-mining workflow for the profiling of phenylfentanyl in vitro metabolites

Illicit fentanyl and analogues have been involved in many fatalities and cases of intoxication across the United States over the last decade, and are becoming a health concern in Europe. New potent analogues emerge onto the drug market every year to circumvent analytical detection and legislation, and little pharmacological/toxicological data are available when the substances first appear. However, pharmacokinetic data are crucial to determine specific biomarkers of consumption in clinical and forensic settings, considering the low active doses and the rapid metabolism of fentanyl analogues. Phenylfentanyl is a novel analogue that was first detected in seized material in 2017, and little is currently known about this substance and its metabolism. We studied phenylfentanyl metabolic fate using in silico predictions with GLORYx freeware, human hepatocyte incubations, and liquid chromatography-high-resolution tandem mass spectrometry (LC-HRMS/MS). We applied a specific targeted/untargeted workflow using data-mining software to allow the rapid and partially automated screening of LC-HRMS/MS raw data. Approximately 90,000 substances were initially individuated after 3-h incubation with hepatocytes, and 115 substances were automatically selected for a manual check by the operators. Finally, 13 metabolites, mostly produced by N-dealkylation, amide hydrolysis, oxidation, and combinations thereof, were identified. We suggest phenylnorfentanyl as the main biological marker of phenylfentanyl use, and we proposed the inclusion of its fragmentation pattern in mzCloud and HighResNPS online libraries. Other major metabolites include N-Phenyl-1-(2-phenylethyl)-4-piperidinamine (4-ANPP), 1-(2-phenylethyl)-4-piperidinol, and other non-specific metabolites. Phase II transformations were infrequent, and the hydrolysis of the biological samples is not required to increase the detection capability of non-conjugated metabolites. The overall workflow is easily adaptable for the metabolite profiling of other novel psychoactive substances.

The metabolism of the synthetic cannabinoids ADB-BUTINACA and ADB-4en-PINACA and their detection in forensic toxicology casework and infused papers seized in prisons

Early warning systems detect new psychoactive substances (NPS), while dedicated monitoring programs and routine drug and toxicology testing identify fluctuations in prevalence. We report the increasing prevalence of the synthetic cannabinoid receptor agonist (SCRA) ADB-BUTINACA (N-[1-amino-3,3-dimethyl-1-oxobutan-2-yl]-1-butyl-1H-indazole-3-carbox-amide). ADB-BUTINACA was first detected in a seizure in Sweden in 2019, and we report its detection in 13 routine Swedish forensic toxicology cases soon after. In January 2021, ADB-BUTINACA was detected in SCRA-infused papers seized in Scottish prisons and has rapidly increased in prevalence, being detected in 60.4% of the SCRA-infused papers tested between January and July 2021. In this work, ADB-BUTINACA was incubated with human hepatocytes (HHeps), and 21 metabolites were identified in vitro, 14 being detected in authentic case samples. The parent drug and metabolites B9 (mono-hydroxylation on the n-butyl tail) and B16 (mono-hydroxylation on the indazole ring) are recommended biomarkers in blood, while metabolites B4 (dihydrodiol formation on the indazole core), B9, and B16 are suitable biomarkers in urine. ADB-4en-PINACA (N-[1-amino-3,3-dimethyl-1-oxobutan-2-yl]-1-[pent-4-en-1-yl]-1H-indazole-3-carboxamide) was detected in Scottish prisons in December 2020, but, unlike ADB-BUTINACA, prevalence has remained low. ADB-4en-PINACA was incubated with HHeps, and 11 metabolites were identified. Metabolites E3 (dihydrodiol formed in the tail moiety) and E7 (hydroxylation on the linked/head group) are the most abundant metabolites in vitro and are suggested as urinary biomarkers. The in vitro potencies of ADB-BUTINACA (EC₅₀ , 11.5 nM and ADB-4en-PINACA (EC₅₀ , 11.6 nM) are similar to that of MDMB-4en-PINACA (EC₅₀ , 4.3 nM). A third tert-leucinamide SCRA, ADB-HEXINACA was also detected in prison samples and warrants further investigation.

Quantification of Major Metabolites of AB-FUBINACA in Solid Tissues Obtained from an Abuser

AB-FUBINACA M3 was reported to be a major metabolite of the drug, but its in vivo concentration in authentic human solid tissues has not been quantified yet. Another metabolite AB-FUBINACA M4 did not receive much attention previously and also has not been quantified yet in any authentic human specimens. The aims of this study are to establish a sensitive method for quantification of M3 and M4 in solid tissues and to compare the metabolite profile of AB-FUBINACA in authentic human specimens in vivo with that produced by human hepatocytes in vitro. The quantification was performed by liquid chromatography (LC)-quadrupole-ion trap-tandem mass spectrometry (MS-MS), and the characterization by LC-quadrupole Orbitrap MS-MS The limits of quantification of M3 were 10 pg/mL and 60 pg/g, and those of M4 were 100 pg/mL and 600 pg/g in urine and tissues, respectively. In the present work, M3 and M4 were identified and quantified in human lung, liver and kidney obtained from a cadaver for the first time; the concentrations of M3 were 226, 255, 202 and 155 pg/mL or g, and those of M4 14,400, 768, 637 and 1,390 pg/mL or g in urine, lung, liver and kidney, respectively. The peak intensity profiles of seven metabolites in these specimens were compared with that produced by human hepatocytes; the top three metabolites in urine specimen were completely different from those of hepatocytes. M3 was reported as the predominant metabolite in several previous works and M4 was listed as a minor metabolite in only one work, but, in this work, M4 has been found to be the major metabolite in all of the authentic urine, lung, liver and kidney specimens. The M3 plus M4 metabolites in lung or kidney were found most recommendable to prove AB-FUBINACA consumption, when urine specimen is lacking.

The key role of mass spectrometry in comprehensive research on new psychoactive substances

New psychoactive substances (NPS) are a wide group of compounds that try to mimic the effects produced by the 'classical' illicit drugs, including cannabis (synthetic cannabinoids), cocaine and amphetamines (synthetic cathinones) or heroin (synthetic opioids), and which health effects are still unknown for most of them. Nowadays, more than 700 compounds are being monitored by official organisms, some of which have been recently identified in seizures and/or intoxication cases. Toxicological analysis plays a pivotal role in NPS research. A comprehensive investigation on NPS, from the first identification of a novel substance until its detection in drug users to help in diagnostics and medical treatment, requires the use of a wide variety of instruments and analytical strategies. This paper illustrates the key role of mass spectrometry (MS) along a comprehensive investigation on NPS. The synthetic cannabinoid XLR-11 and the synthetic cathinone 5-PPDi have been chosen as representative substances of the most consumed NPS families. Moreover, both compounds have been investigated at our laboratory in different stages of the three-step strategy considered in this article. The initial identification and characterisation of the compound in consumption products, the first reported metabolic pathway and the development of analytical methodologies for its determination (and/or their metabolites) in different toxicological samples are described. The analytical strategies and MS instruments are briefly discussed to show the reader the possibilities that MS instrumentation offer to analytical scientists. This publication aims to be a starting point for those interested on the NPS research field from an analytical chemistry point of view.

Current Situation of the Metabolomics Techniques Used for the Metabolism Studies of New Psychoactive Substances

PURPOSE

The purpose of this short overview is to summarize and discuss the English-written and PubMed-listed review articles and original studies published between January 2015 and April 2019 on the use of metabolomics techniques for investigating the metabolism of new psychoactive substances (NPS). First, a brief introduction is given on the metabolism of NPS and metabolomics techniques in general. Afterward, the selected original studies are summarized and discussed. Finally, a section dedicated to the studies on NPS beyond metabolism using metabolomics techniques is provided. Thereafter, both sections are concluded and perspectives are given.

METHODS

PubMed was searched for English-written literature published between January 1, 2015 and April 1, 2019.

RESULTS

The present short overview found that the current use of metabolomics techniques in investigating the metabolism of NPS is rather limited, but these techniques can support and facilitate traditional metabolism studies.

CONCLUSIONS

Thus, there may be a certain potential for using metabolomics techniques in the field of NPS research, but a great challenge remains to thoroughly adopt the existing metabolomics methods.

A Systematic Study of the In Vitro Pharmacokinetics and Estimated Human In Vivo Clearance of Indole and Indazole-3-Carboxamide Synthetic Cannabinoid Receptor Agonists Detected on the Illicit Drug Market

In vitro pharmacokinetic studies were conducted on enantiomer pairs of twelve valinate or tert-leucinate indole and indazole-3-carboxamide synthetic cannabinoid receptor agonists (SCRAs) detected on the illicit drug market to investigate their physicochemical parameters and structure-metabolism relationships (SMRs). Experimentally derived Log D_7.4 ranged from 2.81 (AB-FUBINACA) to 4.95 (MDMB-4en-PINACA) and all SCRAs tested were highly protein bound, ranging from 88.9 ± 0.49% ((R)-4F-MDMB-BINACA) to 99.5 ± 0.08% ((S)-MDMB-FUBINACA). Most tested SCRAs were cleared rapidly in vitro in pooled human liver microsomes (pHLM) and pooled cryopreserved human hepatocytes (pHHeps). Intrinsic clearance (CL_int) ranged from 13.7 ± 4.06 ((R)-AB-FUBINACA) to 2944 ± 95.9 mL min⁻¹ kg⁻¹ ((S)-AMB-FUBINACA) in pHLM, and from 110 ± 34.5 ((S)-AB-FUBINACA) to 3216 ± 607 mL min⁻¹ kg⁻¹ ((S)-AMB-FUBINACA) in pHHeps. Predicted Human in vivo hepatic clearance (CL_H) ranged from 0.34 ± 0.09 ((S)-AB-FUBINACA) to 17.79 ± 0.20 mL min⁻¹ kg⁻¹ ((S)-5F-AMB-PINACA) in pHLM and 1.39 ± 0.27 ((S)-MDMB-FUBINACA) to 18.25 ± 0.12 mL min⁻¹ kg⁻¹ ((S)-5F-AMB-PINACA) in pHHeps. Valinate and tert-leucinate indole and indazole-3-carboxamide SCRAs are often rapidly metabolised in vitro but are highly protein bound in vivo and therefore predicted in vivo CL_H is much slower than CL_int. This is likely to give rise to longer detection windows of these substances and their metabolites in urine, possibly as a result of accumulation of parent drug in lipid-rich tissues, with redistribution into the circulatory system and subsequent metabolism.

Overview of Synthetic Cannabinoids ADB-FUBINACA and AMB-FUBINACA: Clinical, Analytical, and Forensic Implications

ADB-FUBINACA and AMB-FUBINACA are two synthetic indazole-derived cannabinoid receptor agonists, up to 140- and 85-fold more potent, respectively, than trans-∆⁹-tetrahydrocannabinol (∆⁹-THC), the main psychoactive compound of cannabis. Synthesised in 2009 as a pharmaceutical drug candidate, the recreational use of ADB-FUBINACA was first reported in 2013 in Japan, with fatal cases being described in 2015. ADB-FUBINACA is one of the most apprehended and consumed synthetic cannabinoid (SC), following AMB-FUBINACA, which emerged in 2014 as a drug of abuse and has since been responsible for several intoxication and death outbreaks. Here, we critically review the physicochemical properties, detection methods, prevalence, biological effects, pharmacodynamics and pharmacokinetics of both drugs. When smoked, these SCs produce almost immediate effects (about 10 to 15 s after use) that last up to 60 min. They are rapidly and extensively metabolised, being the O-demethylated metabolite of AMB-FUBINACA, 2-(1-(4-fluorobenzyl)-1H-indazole-3-carboxamide)-3-methylbutanoic acid, the main excreted in urine, while for ADB-FUBINACA the main biomarkers are the hydroxdimethylpropyl ADB-FUBINACA, hydroxydehydrodimethylpropyl ADB-FUBINACA and hydroxylindazole ADB-FUBINACA. ADB-FUBINACA and AMB-FUBINACA display full agonism of the CB1 receptor, this being responsible for their cardiovascular and neurological effects (e.g., altered perception, agitation, anxiety, paranoia, hallucinations, loss of consciousness and memory, chest pain, hypertension, tachycardia, seizures). This review highlights the urgent requirement for additional studies on the toxicokinetic properties of AMB-FUBINACA and ADB-FUBINACA, as this is imperative to improve the methods for detecting and quantifying these drugs and to determine the best exposure markers in the various biological matrices. Furthermore, it stresses the need for clinicians and pathologists involved in the management of these intoxications to describe their findings in the scientific literature, thus assisting in the risk assessment and treatment of the harmful effects of these drugs in future medical and forensic investigations.

Pyrrolidinyl Synthetic Cathinones α-PHP and 4F-α-PVP Metabolite Profiling Using Human Hepatocyte Incubations

For more than ten years, new synthetic cathinones (SCs) mimicking the effects of controlled cocaine-like stimulants have flooded the illegal drug market, causing numerous intoxications and fatalities. There are often no data on the pharmacokinetics of these substances when they first emerge onto the market. However, the detection of SC metabolites is often critical in order to prove consumption in clinical and forensic settings. In this research, the metabolite profile of two pyrrolidinyl SCs, α-pyrrolidinohexaphenone (α-PHP) and 4''-fluoro-α-pyrrolidinovalerophenone (4F-α-PVP), were characterized to identify optimal intake markers. Experiments were conducted using pooled human hepatocyte incubations followed by liquid chromatography-high-resolution tandem mass spectrometry and data-mining software. We suggest α-PHP dihydroxy-pyrrolidinyl, α-PHP hexanol, α-PHP 2'-keto-pyrrolidinyl-hexanol, and α-PHP 2'-keto-pyrrolidinyl as markers of α-PHP use, and 4F-α-PVP dihydroxy-pyrrolidinyl, 4F-α-PVP hexanol, 4F-α-PVP 2'-keto-pyrrolidinyl-hexanol, and 4F-α-PVP 2'-keto-pyrrolidinyl as markers of 4F-α-PVP use. These results represent the first data available on 4F-α-PVP metabolism. The metabolic fate of α-PHP was previously studied using human liver microsomes and urine samples from α-PHP users. We identified an additional major metabolite (α-PHP dihydroxy-pyrrolidinyl) that might be crucial for documenting exposure to α-PHP. Further experiments with suitable analytical standards, which are yet to be synthesized, and authentic specimens should be conducted to confirm these results.

Interpol review of toxicology 2016-2019

This review paper covers the forensic-relevant literature in toxicology from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20.Papers%202019.pdf.

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.

New psychoactive substances (NPS) prevalence over LSD in blotter seized in State of Santa Catarina, Brazil: A six-year retrospective study

Designer drugs or new psychoactive substances (NPS) are a heterogeneous group of substances obtained through the modification of chemical structure of some natural products or drugs. NPS illegally commercialized in blotter papers mimicking the most common form of LSD consumption, with a great variability of colours and symbols, have largely increased worldwide, including in Brazil, becoming an important emerging public health issue. In this study, we have evaluated the presence and profile of NPS in blotters seized in the State of Santa Catarina, Brazil, over the period of 2011 to 2017. The state government criminal forensics staff has performed gas chromatography-mass spectrometer (GC-MS) analyses in order to determine the chemical composition of the blotters. During the evaluated period, there was a considerable increase in the seizing of blotters events, from 87 in 2011, to 301 in 2016 and reaching 277 in 2017. There was also an increase in the number of blotters seized per event. Interestingly, while in 2011, 100% of blotters contained LSD, this number decreased to 0,1% in 2014, and achieved 17,6% in 2017, when up to 25 different substances were detected in blotters seized. Drugs such as DOx, NBOMe, fentanyl, mescaline derivatives, triptamines, cathinones, and synthetic cannabinoids were detected and became the major substances found in blotters. In some cases, more than one substance was found in the same blotter, characterizing a new mixture scenario. The presence of several new psychoactive substances in blotters is a reality in forensic toxicology. In Brazil, it might be related to the fact that most of these substances were not considered illegal by Brazilian legislation by the time they emerged.

Fatal intoxication of a regular drug user following N-ethyl-hexedrone and ADB-FUBINACA consumption

In Hungary, N-ethyl-hexedrone (NEH) was the most frequently seized stimulant designer drug in 2017, while among synthetic cannabinoids ADB-FUBINACA and AB-FUBINACA were the most popular. Symptoms of intoxication by these substances are well known but less is known about the pathology of overdose-related death. NEH-induced fatal intoxication has not been described in the literature and knowledge surrounding the particular circumstances of death could be useful better public education of risk and more adequate treatment of overdose patients. In this report, we characterize the case of a 23-year-old male regular drug user who died a few hours after NEH and ADB-FUBINACA consumption. His medical history showed arrhythmia in childhood, and some seizures. Autopsy found he had a BMI of 42.9, a hypertrophic and dilated heart, severe atherosclerosis of the valves, coronaries and the arteries, and edema of the internal organs. Histology confirmed those findings. Postmortem blood levels of NEH were 285 ng/ml, along with 0.08 ng/ml ADB-FUBINACA and five ADB-FUBINACA metabolites. Based on the blood concentrations measured in suspected drug users (≤83.9 ng/ml) we hypothesize that NEH intoxication was the cause of death in this case, with heart disease being a co-factor and that the synthetic cannabinoid effect might have been accompaniment. This case also offered the opportunity to identify the metabolites of ADB-FUBINACA in the blood. We identified metabolites in the post-mortem blood by comparing them to human liver microsomal enzyme metabolites in vitro. Three major and two minor metabolites were found in the blood, of which two could only be derived from ADB-FUBINACA, as opposed to other cannabinoids. The case highlights the importance of the complex analysis of drug related deaths by medico-legal autopsy, histopathology and toxicology.

New Synthetic Cannabinoids Metabolism and Strategies to Best Identify Optimal Marker Metabolites

Synthetic cannabinoids (SCs) were initially developed as pharmacological tools to probe the endocannabinoid system and as novel pharmacotherapies, but are now highly abused. This is a serious public health and social problem throughout the world and it is highly challenging to identify which SC was consumed by the drug abusers, a necessary step to tie adverse health effects to the new drug's toxicity. Two intrinsic properties complicate SC identification, their often rapid and extensive metabolism, and their generally high potency relative to the natural psychoactive Δ9-tetrahydrocannabinol in cannabis. Additional challenges are the lack of reference standards for the major urinary metabolites needed for forensic verification, and the sometimes differing illicit and licit status and, in some cases, identical metabolites produced by closely related SC pairs, i.e., JWH-018/AM-2201, THJ-018/THJ-2201, and BB-22/MDMB-CHMICA/ADB-CHMICA. We review current SC prevalence, establish the necessity for SC metabolism investigation and contrast the advantages and disadvantages of multiple metabolic approaches. The human hepatocyte incubation model for determining a new SC's metabolism is highly recommended after comparison to human liver microsomes incubation, in silico prediction, rat in vivo, zebrafish, and fungus Cunninghamella elegans models. We evaluate SC metabolic patterns, and devise a practical strategy to select optimal urinary marker metabolites for SCs. New SCs are incubated first with human hepatocytes and major metabolites are then identified by high-resolution mass spectrometry. Although initially difficult to obtain, authentic human urine samples following the specified SC exposure are hydrolyzed and analyzed by high-resolution mass spectrometry to verify identified major metabolites. Since some SCs produce the same major urinary metabolites, documentation of the specific SC consumed may require identification of the SC parent itself in either blood or oral fluid. An encouraging trend is the recent reduction in the number of new SC introduced per year. With global collaboration and communication, we can improve education of the public about the toxicity of new SC and our response to their introduction.

Screening methods for rapid determination of new psychoactive substances (NPS) in conventional and non-conventional biological matrices

In the last years, a global awareness has arisen from the reported harmful effects and public health risks associated with the consumption of new psychoactive substances (NPSs). Improving efforts in the detection and identification of these substances have emerged as a global analytical challenge involving the large range of NPSs' chemical structures and the variety of conventional and non-conventional biological matrices. Indeed, detection capabilities and screening tools impact many fields and settings, including seized products analysis, workplace and roadside drug controls, emergency rooms, drug addiction treatment clinics, post-mortem and criminal caseworks, law enforcement and health interventions. Colorimetric, immunochemical and chromatographic-mass spectrometry techniques have been investigated and developed for the rapid identification of NPSs. Considering the continuous emergence of new substances, this review offers a panoramic view on the current status of analytical approaches for the rapid screening of NPSs, including, when available, data on conventional and non-conventional biological matrices. Although some of the presented methods are sound and promising, their applications are still limited, thus proving the importance of further investigations. New screening and sensitive targeted methods for NPS and their metabolites should be developed in different types of biological matrices, where concentration of substances and matrix effects can be significantly different.

The ongoing challenge of novel psychoactive drugs of abuse. Part I. Synthetic cannabinoids (IUPAC Technical Report)

In the past decade, the world has experienced a large increase in the number of novel compounds appearing on the illicit drug market for recreational purposes. Such substances are designed to circumvent governmental regulations; the illegal drug manufacturers take a known psychoactive compound reported in the scientific literature and slightly modify its chemical structure in order to produce analogues that will mimic the pharmacological activity of the original substance. Many of these novel substances are sold via the Internet. Among the various chemical classes, synthetic cannabinoid receptor modulators, commonly referred to as “synthetic cannabinoids” have been at the forefront, as demonstrated by the frequency of drug seizures, numerous severe toxic effects, and fatalities associated with some of these substances. This review presents the chemical structures of relevant synthetic cannabinoids and describes their mechanism of action, pharmacological features, metabolic pathways, and structure-activity relationships. It illustrates the approaches used in forensic testing, both for bulk analysis (drug seizures) and for analytical toxicology (biological matrices) and discusses aspects of regulation surrounding this drug class. This report is intended to provide pertinent information for the purposes of informing scientific, medical, social, and governmental bodies about this ever-evolving recreational drug class and the challenges it poses worldwide.

Toxicokinetics of NPS: Update 2017

This summarizing and descriptive review article is an update on previously published reviews. It covers English-written and PubMed-listed review articles and original studies published between May 2016 and November 2017 on the toxicokinetics of new psychoactive substances (NPS). Compounds covered include stimulants and entactogens, synthetic cannabinoids, tryptamines, phenethylamine and phencyclidine-like drugs, benzodiazepines, and opioids. First, an overview and discussion is provided on selected review articles followed by an overview and discussion on selected original studies. Both sections are then concluded by an opinion on these latest developments. The present review shows that the NPS market is still highly dynamic and that studies regarding their toxicokinetics are necessary to understand risks associated with their consumption. Data collection and studies are encouraged to allow for detection of NPS in biological matrices in cases of acute intoxications or chronic consumption. Although some data are available, scientific papers dealing with the mechanistic reasons behind acute and chronic toxicity are still lacking.

Human Hepatocyte Metabolism of Novel Synthetic Cannabinoids MN-18 and Its 5-Fluoro Analog 5F-MN-18

BACKGROUND

In 2014, 2 novel synthetic cannabinoids, MN-18 and its 5-fluoro analog, 5F-MN-18, were first identified in an ongoing survey of novel psychoactive substances in Japan. In vitro pharmacological assays revealed that MN-18 and 5F-MN-18 displayed high binding affinities to human CB₁ and CB₂ receptors, with K_i being 1.65-3.86 nmol/L. MN-18 and 5F-MN-18 were scheduled in Japan and some other countries in 2014. Despite increasing prevalence, no human metabolism data are currently available, making it challenging for forensic laboratories to confirm intake of MN-18 or 5F-MN-18.

METHODS

We incubated 10 μmol/L of MN-18 and 5F-MN-18 in human hepatocytes for 3 h and analyzed the samples on a TripleTOF 5600⁺ high-resolution mass spectrometer to identify appropriate marker metabolites. Data were acquired via full scan and information-dependent acquisition-triggered product ion scans with mass defect filter.

RESULTS

In total, 13 MN-18 metabolites were detected, with the top 3 abundant metabolites being 1-pentyl-1H-indazole-3-carboxylic acid, pentyl-carbonylated MN-18, and naphthalene-hydroxylated MN-18. For 5F-MN-18, 20 metabolites were observed, with the top 3 abundant metabolites being 5'-OH-MN-18, MN-18 pentanoic acid, and 1-(5-fluoropentyl)-1H-indazole-3-carboxylic acid.

CONCLUSIONS

We have characterized MN-18 and 5F-MN-18 metabolism with human hepatocytes and high-resolution mass spectrometry, and we recommend characteristic major metabolites for clinical and forensic laboratories to identify MN-18 and 5F-MN-18 intake and link observed adverse events to these novel synthetic cannabinoids.