Metabolic profiling of synthetic cannabinoid 5F-ADB by human liver microsome incubations and urine samples using high-resolution mass spectrometry

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.

Human phase-I metabolism and prevalence of two synthetic cannabinoids bearing an ethyl ester moiety: 5F-EDMB-PICA and EDMB-PINACA

Around 2017, with the appearance of 5F-EDMB-PINACA, synthetic cannabinoids (SCs) carrying an ethyl ester moiety at the linked group started spreading on the market of new psychoactive substances (NPS). In 2020 and 2021, the indole analog of 5F-EDMB-PINACA (5F-EDMB-PICA) and the non-fluorinated analog of this compound (EDMB-PINACA) were analytically characterized. Here, we present suitable urinary markers to prove the consumption of these two ethyl analogs. Ten authentic urine samples for each compound were analyzed by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-qToF-MS). Anticipated phase-I metabolites detected in urine samples were confirmed in vitro by applying a pooled human liver microsomes (pHLM) assay. Prevalence data were obtained from urines collected for abstinence control and submitted to a screening method for SC metabolites. Ten phase-I metabolites of 5F-EDMB-PICA and 18 of EDMB-PINACA were detected by LC-qToF-MS analysis of authentic urine specimens. The main in-vivo metabolites were built by ester hydrolysis, often coupled to further metabolic processes. Investigation of phase-I biotransformation led to the identification of ester hydrolysis, monohydroxylation, and defluorination products as the most suitable urinary biomarkers for 5F-EDMB-PICA. Metabolites formed by ester hydrolysis coupled to ketone formation and by monohydroxylation are suggested for the detection of EDMB-PINACA. From October 1, 2020 to February 1, 2022, among positive urine samples, 5.4% and 10.1% tested positive 5F-EDMB-PICA and EDMB-PINACA, respectively. Due to common metabolites shared among structurally related SCs, the unequivocal detection of their consumption remains challenging for forensic laboratories and requires sensitive methods to monitor multiple metabolites, ideally including highly specific species.

Transesterification of Indazole-3-carboxamide Synthetic Cannabinoids: Identification of Metabolite Biomarkers for Diagnosing Co-abuse of 5F-MDMB-PINACA and Alcohol

Concurrent use of alcohol with synthetic cannabinoids (SCs) has been widely recorded among drug abusers. The susceptibilities of three indazole-3-carboxamide type SCs with methyl ester moiety, 5F-MDMB-PINACA, 5F-MMB-PINACA, and MMB-FUBINACA, to transesterification in the presence of ethanol warranted further investigation in view of probable augmented toxicity. In vitro metabolite identification experiments were first performed using human liver microsomes (HLMs) to characterize the novel metabolites of the three parent SCs in the presence of ethanol. Formation of transesterified metabolite, hydrolyzed metabolite, and several oxidative metabolites in HLM in the presence of alcohol was further determined for each parent SC and the respective ethyl ester analog, 5F-EDMB-PINACA, 5F-EMB-PINACA, and EMB-FUBINACA, to quantitatively elucidate transesterification and hydrolysis activities. Our results suggested that all three SCs undergo carboxylesterase-mediated transesterification to their respective ethyl ester analog in the presence of ethanol, which was incubation time- and ethanol concentration-dependent. Each ethyl ester metabolite was sequentially and readily metabolized to novel oxidative metabolites with the intact ethyl ester moiety and the same hydrolyzed metabolite as derived from its parent SC. A smaller extent of transesterification was non-enzymatically driven. Notably, we proposed 5F-EDMB-PINACA oxidative defluorination metabolite as the biomarker for diagnosing the potential co-abuse of 5F-MDMB-PINACA and alcohol. Due to the comparable pharmacological activities between each SC and its ethyl ester metabolite, augmented toxicity associated with co-abuse of SCs and alcohol is probable and deserves further investigation.

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.

Detection of the Synthetic Cannabinoids AB-CHMINACA, ADB-CHMINACA, MDMB-CHMICA, and 5F-MDMB-PINACA in Biological Matrices: A Systematic Review

Simple Summary

Synthetic cannabinoids were originally developed for scientific research and potential therapeutic agents. However, clandestine laboratories synthesize them and circumvent legal barriers by falsely marketing them as incense or herbal products. They have serious adverse effects, and new derivatives are continuously found in the market, making their detection difficult due to the lack of comparative standards. Human matrices are used to identify the type of synthetic cannabinoid and the time of its consumption. This review discusses the use of hair, oral fluid, blood, and urine in the detection and quantification of some of the major synthetic cannabinoids. Based on the results, some recommendations can be followed, for example, the use of hair to detect chronic and retrospective consumption (although sensitive to external contamination) and oral fluid or blood for the simultaneous detection of the parent compounds and their metabolites. If longer detection times than blood or oral fluid are needed, urine is the matrix of choice, although its pH may intervene in the analysis. This work highlights the use of new techniques, such as high-resolution mass spectrometry, to avoid the use of previous standards and to monitor new trends in the drug market.

Abstract

New synthetic cannabinoids (SCs) are emerging rapidly and continuously. Biological matrices are key for their precise detection to link toxicity and symptoms to each compound and concentration and ascertain consumption trends. The objective of this study was to determine the best human biological matrices to detect the risk-assessed compounds provided by The European Monitoring Centre for Drugs and Drug Addiction: AB-CHMINACA, ADB-CHMNACA, MDMB-CHMICA, and 5F-MDMB-PINACA. We carried out a systematic review covering 2015 up to the present date, including original articles assessing detection in antemortem human biological matrices with detailed validation information of the technique. In oral fluid and blood, SC parent compounds were found in oral fluid and blood at low concentrations and usually with other substances; thus, the correlation between SCs concentrations and severity of symptoms could rarely be established. When hair is used as the biological matrix, there are difficulties in excluding passive contamination when evaluating chronic consumption. Detection of metabolites in urine is complex because it requires prior identification studies. LC-MS/MS assays were the most widely used approaches for the selective identification of SCs, although the lack of standard references and the need for revalidation with the continuous emergence of new SCs are limiting factors of this technique. A potential solution is high-resolution mass spectrometry screening, which allows for non-targeted detection and retrospective data interrogation.

Analytical findings in a non-fatal intoxication with the synthetic cannabinoid 5F-ADB (5F-MDMB-PINACA): a case report

The case report centres on analytical findings from a spice sample (mixed with tobacco (as a cigarette) for consumption), and its corresponding plasma sample, smoked by a 31-year-old man who was attended by emergency services following collapse. The man was fully conscious and cooperative during initial medical treatment. Suddenly, he suffered a complete loss of self-control, whereupon the police was notified. The man encountered the police officers when exiting the apartment, at which point he threatened them with clenched fists and reached for a plant bucket in order to strike out in the direction of the officers. At the trial, he described himself as confused and as being completely overwhelmed, having lost self-control, suffered a panic attack and “just wanted to get out the situation”. Furthermore, he stated that he had no recollection of the incident. He feared death due to palpitations, heart pain, dizziness and repetitive anxiety states. Routine systematic as well as extended toxicological analysis of the plasma sample, taken approximately 2 h after the incident, confirmed the use of cannabis and spice. Plasma concentrations of THC, OH-THC and THC-COOH were 8.0 μg/L, 4.0 μg/L and 147 μg/L, respectively. Furthermore, analysis confirmed uptake of 5F-ADB (5F-MDMB-PINACA) via detection of both 5F-ADB and the 5F-ADB N-(5-OH-pentyl) metabolite. The spice sample additionally contained 5F-MDMB-PICA, which was not detected in the plasma sample. A differentiation between a possible co-use and a recent use of cannabis was not possible. In summary, this case once more underlines the health risks of spice use.

Synthetic cannabinoid receptor agonists and their human metabolites in sewage water: Stability assessment and identification of transformation products

Since their first appearance in 2008, synthetic cannabinoid receptor agonists (SCRAs) remain the most popular new psychoactive substances (NPS) in the EU. Following consumption, these drugs and their metabolites are urinary excreted and enter the sewage system enabling the application of wastewater-based epidemiology (WBE). Knowing the fate of target analytes in sewage water is essential for successful application of WBE. This study investigates the stability of several chemically diverse SCRAs and selected human metabolites under sewage conditions utilizing a combination of liquid chromatography-tandem mass spectrometry and high-resolution mass spectrometry (HRMS). Target analytes included SCRAs with indole (5F-PB-22, PB-22 pentanoic acid), indazole (AMB-FUBINACA, 5F-ADB, 5F-ADB dimethylbutanoic acid), carbazole (MDMB-CHMCZCA, EG-018), and γ-carboline (Cumyl-PeGaClone) chemical core structures representing most of the basic core structures that have occurred up to now. Stability tests were performed using wastewater effluent containing 5% activated sludge as inoculum to monitor degradation processes and formation of transformation products (TPs). The majority of investigated SCRAs, excluding the selected human metabolites, was recalcitrant to microbial degradation in sewage systems over a period of 29 days. Their stability was rather controlled by physico-chemical processes like sorption and hydrolysis. Considering a typical hydraulic in-sewer retention time of 24 h, the concentration of AMB-FUBINACA decreased by 90% thus representing the most unstable SCRA investigated in this study. Among the 10 newly identified TPs, three could be considered as relevant markers and should be included into future WBE studies to gain further insight into use and prevalence of SCRAs on the drug market.

Determination of Third-Generation Synthetic Cannabinoids in Oral Fluids

A procedure has been developed for the determination of third-generation synthetic cannabinoids in oral fluid samples by using a semi-automated microextraction by packed sorbent (MEPS) procedure and gas chromatography-mass spectrometry (GC-MS) determination. Five synthetic cannabinoids were employed as model compounds 5F-ADB, MMB-CHMICA, THJ-2201, CUMYL-4CN-BINACA and MDMB-CHMCZCA. The most adequate operative conditions for MEPS were evaluated giving quantitative recoveries, from 89 to 124%, in synthetic and field saliva samples spiked with 125 and 250 μg/L of the studied cannabinoids, with the exception of MDMB-CHMCZCA in field saliva samples that provided slightly lower recoveries from 62 to 66%. A high sensitivity was obtained for the proposed MEPS-GC-MS procedure with limits of detection from 10 to 20 μg/L. The obtained results demonstrate the high potential of MEPS-GC-MS combination for semi-automated, selective and sensitive determination of synthetic cannabinoids in oral fluid samples.

Involuntary 5F-ADB-related intoxication following e-cigarette use

The detection of synthetic cannabinoid (SC) intoxication cases is challenging, even more when the involved SC identification is requested in a forensic context. This situation can be complicated by new modes of SC consumption, non-specific symptomatology, and analytical pitfalls. To illustrate these issues, we report the case of a 16-year-old man who presented symptoms evocating of a seizure disorder in the minutes following the use of a friend's e-cigarette. At admission in the emergency department, his electroencephalogram was interpreted as coherent with a recent seizure episode. 5F-ADB, a third generation SC, was detected in the e-liquid and in an early collected (H2 after the e-cigarette use) serum sample (0.50 µg/L), but not in urine samples (H18 and H38). One 5F-ADB metabolite, O-desmethyl-5F-ADB (M5), was detectable in urine up to at least 38 h after intoxication. Neither 5F-ADB nor its metabolites could be detected in victim's hair sampled 3 months after the intoxication. Although leading to a non-specific symptomatology, acute SC intoxication should be considered when the case history is related to e-cigarette or e-liquid use. Early biological samples are recommended, even if analytical screening can be positive for SC metabolites in urine sampled until 2 days after exposure. Accordingly, data from the literature and the present case underscore the relevance of adding both main 5F-ADB metabolites (M5 and 5-OH-pentyl-ADB) to mass spectrum databases used for toxicological screening in order to reduce the risk of false-negative results in intoxication cases involving 5F-ADB.

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.

Evaluation of Synthetic Cannabinoid Metabolites in Human Blood in the Absence of Parent Compounds: A Stability Assessment

Synthetic cannabinoids represent a chemically diverse class of novel psychoactive substances (NPS) responsible for large analytical and interpretative challenges for forensic toxicologists. Between 2016 and 2019, the three most prevalent synthetic cannabinoids in the United States were MMB-FUBINACA (FUB-AMB), 5F-MDMB-PINACA (5F-ADB) and 5F-MDMB-PICA, based on results from seized drug and toxicology testing. In 2018, accurate determination of synthetic cannabinoid positivity was brought into question as it was determined that the metabolites of these drug species were present in the absence of parent compounds in forensically relevant blood samples. During this study, the stability of MMB-FUBINACA, 5F-MDMB-PINACA and 5F-MDMB-PICA was evaluated, as well as the characterization of breakdown products. A liquid-liquid extraction method was assessed for recovery of basic parent compounds and acidic metabolites and deemed fit for use in this study. Analysis was performed by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) using a SCIEX TripleTOF® 5600+. All three synthetic cannabinoids were found to be unstable when stored in blood at either room temperature or refrigerated; all analytes were considerably more stable when stored in the freezer. All three synthetic cannabinoids degraded to their respective butanoic acid metabolites: MMB-FUBINACA 3-methylbutanoic acid, 5F-MDMB-PINACA 3,3-dimethylbutanoic acid and 5F-MDMB-PICA 3,3-dimethylbutanoic acid. All three of these metabolites were studied and determined to be stable in blood at all storage conditions. Considering these results, our laboratory continued testing for synthetic cannabinoid metabolites in blood samples and found 83 positives (21%) for only a synthetic cannabinoid metabolite. A case report is presented herein where 5F-MDMB-PINACA 3,3-dimethylbutanoic acid was identified in the absence of 5F-MDMB-PINACA. Forensic toxicologists should be aware of the results of this study as they directly impact analytical consideration for test development and implementation, as well as interpretation of findings.

In Vitro Phase I Metabolism of the Recently Emerged Synthetic MDMB-4en-PINACA and Its Detection in Human Urine Samples

MDMB-4en-PINACA (methyl (S)-3,3-dimethyl-2-(1-(pent-4-en-1-yl)-1H-indazole-3-carboxamido)butanoate) is a recently emerged synthetic cannabinoid in Turkey. MDMB-4en-PINACA was detected in herbal material investigated by the Council of Forensic Medicine, Istanbul Narcotics Department in Turkey in April 2019. MDMB-4en-PINACA was added to the drug abuse list and quickly reported in biological samples after its first detection. In this study, the in vitro metabolism of MDMB-4en-PINACA was investigated by using a pooled human liver microsomes (HLMs) assay and liquid chromatography-high-resolution mass spectrometry (LC-HRMS). MDMB-4en-PINACA (5 μmol/L) was incubated with HLMs for up to 1 h, and the metabolites were identified using LC-HRMS and software-assisted data mining. The in vivo metabolism was investigated by the analysis of 22 authentic urine samples and compared to the data received from the in vitro metabolism study. Less than 7.5% of the MDMB-4en-PINACA parent compound remained after the 1 h incubation. We identified 14 metabolites, which were formed via double bond oxidation, ester hydrolysis, N-dealkylation, hydroxylation, dehydrogenation and further oxidation to N-pentanoic acid or a combination of these reactions in vitro. In 10 urine samples (total n = 22), MDMB-4en-PINACA was detected as the parent drug. Three of the identified main metabolites, double bond oxidation in combination with ester hydrolysis and hydroxylation metabolite (M3), MDMB-4en-PINACA butanoic acid (M14) and monohydroxypentyl-MDMB-4en-PINACA (M12), were suggested as suitable urinary markers. In vitro screening of 2,150 authentic urine samples for these identified MDMB-4en-PINACA metabolites resulted in 56 cases of confirmed MDMB-4en-PINACA consumption (2.6%).

Monitoring metabolism of synthetic cannabinoid 4F-MDMB-BINACA via high-resolution mass spectrometry assessed in cultured hepatoma cell line, fungus, liver microsomes and confirmed using urine samples

Purpose

A tert-leucinate derivative synthetic cannabinoid, methyl (2S)-2-([1-(4-fluorobutyl)-1H-indazole-3-carbonyl]amino)-3,3-dimethylbutanoate (4F-MDMB-BINACA, 4F-MDMB-BUTINACA or 4F-ADB) is known to adversely impact health. This study aimed to evaluate the suitability of three different modes of monitoring metabolism: HepG2 liver cells, fungus Cunninghamella elegans (C. elegans) and pooled human liver microsomes (HLM) for comparison with human in-vivo metabolism in identifying suitable urinary marker(s) for 4F-MDMB-BINACA intake.

Methods

Tentative structure elucidation of in-vitro metabolites was performed on HepG2, C. elegans and HLM using liquid chromatography–tandem mass spectrometry and high-resolution mass spectrometry analysis. In-vivo metabolites obtained from twenty authentic human urine samples were analysed using liquid chromatography–Orbitrap mass spectrometry.

Results

Incubation with HepG2, C. elegans and HLM yielded nine, twenty-three and seventeen metabolites of 4F-MDMB-BINACA, respectively, formed via ester hydrolysis, hydroxylation, carboxylation, dehydrogenation, oxidative defluorination, carbonylation or reaction combinations. Phase II metabolites of glucosidation and sulfation were also exclusively identified using C. elegans model. Eight in-vivo metabolites tentatively identified were mainly products of ester hydrolysis with or without additional dehydrogenation, N-dealkylation, monohydroxylation and oxidative defluorination with further oxidation to butanoic acid. Metabolites with intact terminal methyl ester moiety, i.e., oxidative defluorination with further oxidation to butanoic acid, were also tentatively identified.

Conclusions

The in-vitro models presented proved useful in the exhaustive metabolism studies. Despite limitations, HepG2 identified the major 4F-MDMB-BINACA ester hydrolysis metabolite, and C. elegans demonstrated the capacity to produce a wide variety of metabolites. Both C. elegans and HLM produced all the in-vivo metabolites. Ester hydrolysis and ester hydrolysis plus dehydrogenation 4F-MDMB-BINACA metabolites were recommended as urinary markers for 4F-MDMB-BINACA intake.

Metabolic profiling of synthetic cannabinoid 5F-ADB and identification of metabolites in authentic human blood samples via human liver microsome incubation and ultra-high-performance liquid chromatography/high-resolution mass spectrometry

RATIONALE

Indazole carboxamide synthetic cannabinoids, a prevalent class of recreational drugs, are a major clinical, forensic and public health challenge. One such compound, 5F-ADB, has been implicated in fatalities worldwide. Understanding its metabolism and distribution facilitates the development of laboratory assays to substantiate its consumption. Synthetic cannabinoid metabolites have been extensively studied in urine; studies identifying metabolites in blood are limited and no data on the metabolic stability (half-life, clearance and extraction ratio) of 5F-ADB have been published prior to this report.

METHODS

The in vitro metabolism of 5F-ADB was elucidated via incubation with human liver microsomes for 2 h at 37°C. Samples were collected at multiple time points to determine its metabolic stability. Upon identification of metabolites, authentic forensic human blood samples underwent liquid-liquid extraction and were screened for metabolites. Extracts were analyzed via ultra-high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UHPLC/QTOFMS) operated in positive electrospray ionization mode.

RESULTS

Seven metabolites were identified including oxidative defluorination (M1); carboxypentyl (M2); monohydroxylation of the fluoropentyl chain (M3.1/M3.2) and indazole ring system (M4); ester hydrolysis (M5); and ester hydrolysis with oxidative defluorination (M6). The half-life (3.1 min), intrinsic clearance (256.2 mL min^-1  kg^-1 ), hepatic clearance (18.6 mL min^-1 kg^-1 ) and extraction ratio (0.93) were determined for the first time. In blood, M1 was present in each sample as the most abundant substance; two samples contained M5; one contained 5F-ADB, M1 and M5.

CONCLUSIONS

5F-ADB is rapidly metabolized in HLM. 5F-ADB, M1 and M5 are pharmacologically active at the cannabinoid receptors (CB₁ /CB₂ ) and M1 and M5 may contribute to a user's impairment profile. The results demonstrate that it is imperative that synthetic cannabinoid assays screen for pharmacologically active metabolites, especially for drugs with short half-lives. The authors propose that M1 and M5 are appropriate markers to include in laboratory blood tests screening for 5F-ADB.

Diagnosing intake and rationalizing toxicities associated with 5F-MDMB-PINACA and 4F-MDMB-BINACA abuse

5F-MDMB-PINACA and 4F-MDMB-BINACA are synthetic cannabinoids (SCs) that elicit cannabinoid psychoactive effects. Defining pharmacokinetic-pharmacodynamic (PK-PD) relationships governing SCs and their metabolites are paramount to investigating their in vivo toxicological outcomes. However, the disposition kinetics and cannabinoid receptor (CB) activities of the primary metabolites of SCs are largely unknown. Additionally, reasons underlying the selection of ester hydrolysis metabolites (EHMs) as urinary biomarkers are often unclear. Here, metabolic reaction phenotyping was performed to identify key metabolizing enzymes of the parent SCs. Hepatic clearances of parent SCs and their EHMs were estimated from microsomal metabolic stability studies. Renal clearances were simulated using a mechanistic kidney model incorporating in vitro permeability and organic anionic transporter 3 (OAT3)-mediated uptake data. Overall clearances were considered in tandem with estimated volumes of distribution for in vivo biological half-lives (t_1/2) predictions. Interactions of the compounds with CB1 and CB2 were investigated using a G-protein coupled receptor activation assay. We demonstrated that similar enzymatic isoforms were implicated in the metabolism of 5F-MDMB-PINACA and 4F-MDMB-BINACA. Our in vivo t_1/2 determinations verified the rapid elimination of parent SCs and suggest prolonged circulation of their EHMs. The pronounced attenuation of the potencies and efficacies of the metabolites against CB1 and CB2 further suggests how toxic manifestations of SC abuse are likely precipitated by augmented exposure to parent SCs. Notably, basolateral OAT3-mediated uptake of the EHMs substantiates their higher urinary abundance. These novel insights underscore the importance of mechanistic, quantitative and systematic characterization of PK-PD relationships in rationalizing the toxicities of SCs.

Comparison of in vitro and in vivo models for the elucidation of metabolic patterns of 7-azaindole-derived synthetic cannabinoids exemplified using cumyl-5F-P7AICA

Due to the dynamic market involving synthetic cannabinoids (SCs), the determination of analytical targets is challenging in clinical and forensic toxicology. SCs usually undergo extensive metabolism, and therefore their main metabolites must be identified for the detection in biological matrices, particularly in urine. Controlled human studies are usually not possible for ethical reasons; thus, alternative models must be used. The aim of this work was to predict the in vitro and in vivo metabolic patterns of 7-azaindole-derived SCs using 1-(5-fluoropentyl)-N-(2-phenylpropan-2-yl)-1H-pyrollo[2,3-b]pyridin-3-carboxamide (cumyl-5F-P7AICA) as an example. Different in vitro (pooled human liver S9 fraction, pooled human liver microsomes, and pig liver microsomes) and in vivo (rat and pig) systems were compared. Monooxygenase isoenzymes responsible for the most abundant phase I steps, namely oxidative defluorination (OF) followed by carboxylation, monohydroxylation, and ketone formation, were identified. In both in vivo models, OF/carboxylation and N-dealkylation/monohydroxylation/sulfation could be detected. Regarding pHS9 and pig urine, monohydroxylation/sulfation or glucuronidation was also abundant. Furthermore, the parent compound could still be detected in all models. Initial monooxygenase activity screening revealed the involvement of CYP2C19, CYP3A4, and CYP3A5. Therefore, in addition to the parent compound, the OF/carboxylated and monohydroxylated (and sulfated or glucuronidated) metabolites can be recommended as urinary targets. In comparison to literature, the pig model predicts best the human metabolic pattern of cumyl-5F-P7AICA. Furthermore, the pig model should be suitable to mirror the time-dependent excretion pattern of parent compounds and metabolites.

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.

In Vitro Metabolic Profile Elucidation of Synthetic Cannabinoid APP-CHMINACA (PX-3)

Indazole carboxamide synthetic cannabinoids remain the most prevalent subclass of new psychoactive substances (NPS) reported internationally. However, the metabolic and pharmacological properties of many of these compounds remain unknown. Elucidating these characteristics allows members of the clinical and forensic communities to identify causative agents in patient samples, as well as render conclusions regarding their toxic effects. This work presents a detailed report on the in vitro phase I metabolism of indazole carboxamide synthetic cannabinoid APP-CHMINACA (PX-3). Incubation of APP-CHMINACA with human liver microsomes, followed by analysis of extracts via high-resolution mass spectrometry, yielded 12 metabolites, encompassing 7 different metabolite classes. Characterization of the metabolites was achieved by evaluating the product ion spectra, accurate mass and chemical formula generated for each metabolite. The predominant biotransformations observed were hydrolysis of the distal amide group and hydroxylation of the cyclohexylmethyl (CHM) substituent. Nine metabolites were amide hydrolysis products, of which five were monohydroxylated, one dihydroxylated and two were ketone products. The metabolites in greatest abundance in the study were products of amide hydrolysis with no further biotransformation (M1), followed by amide hydrolysis with monohydroxylation (M2.1). Three APP-CHMINACA-specific metabolites were generated, all of which were hydroxylated on the CHM group; one mono-, di- and tri-hydroxylated metabolite each was produced, with dihydroxylation (M6) present in the greatest abundance. The authors propose that metabolites M1, M2.1 and M6 are the most appropriate markers to determine consumption of APP-CHMINACA. The methods used in the current study have broad applicability and have been used to determine the in vitro metabolic profiles of multiple synthetic cannabinoids and other classes of NPS. This research can be used to guide analytical scientists in method development, synthesis of reference material, pharmacological testing of proposed metabolites and prediction of metabolic processes of compounds yet to be studied.

Phase I metabolism of synthetic cannabinoid receptor agonist PX-1 (5F-APP-PICA) via incubation with human liver microsomes and UHPLC-HRMS

Studies of the metabolic and pharmacological profiles of indole carboxamide synthetic cannabinoids (a prevalent class of new psychoactive substances) are critical in ensuring that their use can be detected through bioanalytical testing. We have determined the in vitro Phase I metabolism of one such compound, PX-1 (5F-APP-PICA), and appropriate markers to demonstrate human consumption. PX-1 was incubated with human liver microsomes, followed by analysis of the extracts via high-resolution mass spectrometry. A total of 10 metabolites were identified, with simultaneous defluorination and monohydroxylation of the pentyl side chain as the primary biotransformation product (M1). Additional metabolites formed were hydroxylation products of the indole and benzyl moieties, distal amide hydrolysis, N-desfluoropentyl, and carboxypentyl metabolites. Three monohydroxylated metabolites specific to PX-1 were identified and are reported for the first time in this study. The primary metabolite, M1, was further oxidized to M5, a carboxypentyl metabolite. M8 is PX-1 specific, possessing an intact fluoropentyl side chain. These three metabolites are the most suitable for implementation into bioanalytical assays for demonstrating PX-1 consumption. The findings of this study can be used by analytical scientists and medical professionals to determine PX-1 ingestion and predict the metabolites of synthetic cannabinoids sharing structural elements.

In vitro metabolism of the synthetic cannabinoids PX-1, PX-2, and PX-3 by high-resolution mass spectrometry and their clearance rates in human liver microsomes

RATIONALE

N-(1-Amino-1-oxo-3-phenylpropan-2-yl)-1-(5-fluoropentyl)-1H-indole-3-carboxamine (PX-1), N-(1-amino-1-oxo-3-phenylpropan-2-yl)-1-(5-fluoropentyl)-1H-indazole-3-carboxamide (PX-2), and N-(1-amino-1-oxo-3-phenylpropan-2-yl)-1-(cyclohexylmethyl)-1H-indazole-3-carboxamide (PX-3) are scheduled synthetic cannabinoids (SCs). Due to the lack of metabolism data and the extensive metabolism of SCs, consumption of these illicit substances is challenging to prove. The aim of this study was to investigate the metabolism of PX-1, PX-2, and PX-3 and propose marker metabolites to confirm their use.

METHODS

PX-1, PX-2, and PX-3 were incubated in pooled human liver microsomes (HLM) to evaluate the phase I metabolites which were identified using a Q-Exactive hybrid quadrupole-Orbitrap mass spectrometer. Metabolic stability studies were also performed to investigate the half-life and clearance rates using an Agilent 6470A triple quadrupole mass spectrometer.

RESULTS

The calculated half-lives were 15.1 ± 1.02, 3.4 ± 0.27, and 5.2 ± 0.89 min for PX-1, PX-2, and PX-3, respectively, in HLM. The calculated intrinsic clearance values were 0.046, 0.202, and 0.133 mL/min/mg for PX-1, PX-2, and PX-3, respectively. Four metabolites of PX-1, six metabolites of PX-2, and five phase I metabolites of PX-3 were detected. Oxidative deamination was the common biotransformation between the three compounds and there were no common metabolites.

CONCLUSIONS

The metabolic profiles of PX-1, PX-2, and PX-3 provide valuable information for the detection of their metabolites in forensic samples.

Detection and characterization of the new synthetic cannabinoid APP-BINACA in forensic casework

New psychoactive substances (NPS) continue to emerge around the world. APP-BINACA (or APP-BUTINACA), a novel synthetic cannabinoid, was first reported in Europe in January 2019 and later in the United States in March 2019. APP-BINACA was identified in the United States for the first time in blood sample extracts from forensic casework by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). To date, APP-BINACA has been identified in 11 forensic toxicology cases from five states and in both medicolegal death investigations and drug impaired driving investigations. APP-BINACA was commonly found in combination with 4F-MDMB-BINACA. Subsequent to its discovery in biological samples, APP-BINACA was detected and characterized in seized drug material by gas chromatography mass spectrometry (GC-MS), LC-QTOF-MS, and nuclear magnetic resonance (NMR) spectroscopy. Further analysis of biological specimens resulted in the identification of five metabolites, including 4-HO-APP-BINACA and APP-BINACA 3-phenylpropanoic acid. The frequency of APP-BINACA detection appears to be increasing and this new synthetic cannabinoid has been identified as a possible contributory factor in adverse events, including death. This is the first literature report regarding the characterization of the new synthetic cannabinoid APP-BINACA in humans. Since it is not widely tested for, it is not yet known the extent to which APP-BINACA is contributing to morbidity and mortality, but forensic scientists, public health officials, and others should be aware of its possible presence and impact. Laboratories should incorporate APP-BINACA into testing workflows for detection and confirmation, where possible.

5F-MDMB-PICA metabolite identification and cannabinoid receptor activity

According to the European Monitoring Center for Drugs and Drug Addiction (EMCDDA), there were 179 different synthetic cannabinoids reported as of 2017. In the USA, 5F-MDMB-PINACA, or 5F-ADB, accounted for 28% of cannabinoid seizures 2016-2018. The synthetic cannabinoid, 5F-MDMB-PICA, is structurally similar to 5F-MDMB-PINACA with an indole group replacing the indazole. Limited data exist from in vivo or in vitro metabolic studies of these synthetic cannabinoids, so potential metabolites to identify use may be missed. The goals of this study were to (a) investigate 5F-MDMB-PICA and 5F-MDMB-PINACA in vitro metabolism utilizing human hepatocytes; (b) to verify in vitro metabolites by analyzing authentic case specimens; and (c) to identify the potency and efficacy of 5F-MDMB-PICA and 5F-MDMB-PINACA by examining activity at the CB₁ receptor. Biotransformations found in this study included phase I transformations and phase II transformations. A total of 22 5F-MDMB-PICA metabolites (A1 to A22) were identified. From hepatocyte incubations and urine samples, 21 metabolites (B1 to B21) were identified with 3 compounds unique to urine specimens for 5F-MDMB-PINACA. Phase II glucuronides were identified in 5F-MDMB-PICA (n = 3) and 5F-MDMB-PINACA (n = 5). For both compounds, ester hydrolysis and ester hydrolysis in combination with oxidative defluorination were the most prevalent metabolites produced in vitro. Additionally, the conversion of ester hydrolysis with oxidative defluorination to pentanoic acid for the first time was identified for 5F-MDMB-PICA. Therefore, these metabolites would be potentially good biomarkers for screening urine of suspected intoxication of 5F-MDMB-PICA or 5F-MDMB-PINACA. Both 5F-MDMB-PICA and 5F-MDMB-PINACA were acting as full agonists at the CB₁ receptor with higher efficacy and similar potency as JWH-018.

In vitro Phase I metabolism of indazole carboxamide synthetic cannabinoid MDMB-CHMINACA via human liver microsome incubation and high-resolution mass spectrometry

Synthetic cannabinoids have proliferated over the last decade and have become a major public health and analytical challenge, critically impacting the clinical and forensic communities. Indazole carboxamide class synthetic cannabinoids have been particularly rampant, and exhibit severe toxic effects upon consumption due to their high binding affinity and potency at the cannabinoid receptors (CB₁ and CB₂ ). MDMB-CHMINACA, methyl 2-[1-(cyclohexylmethyl)-1H-indazole-3-carboxamido]-3,3-dimethylbutanoate, a compound of this chemical class, has been identified in forensic casework and is structurally related to several other synthetic cannabinoids. This study presents the first extensive report on the Phase I metabolic profile of MDMB-CHMINACA, a potent synthetic cannabinoid. The in vitro metabolism of MDMB-CHMINACA was determined via incubation with human liver microsomes and high-resolution mass spectrometry. The accurate masses of precursor and fragments, mass error (ppm), and chemical formula were obtained for each metabolite. Twenty-seven metabolites were identified, encompassing twelve metabolite types. The major biotransformations observed were hydroxylation and ester hydrolysis. Hydroxylations were located predominantly on the cyclohexylmethyl (CHM) moiety. Ester hydrolysis was followed by additional biotransformations, including dehydrogenation; mono- and dihydroxylation and ketone formation, each with dehydrogenation. Minor metabolites were identified and reported. The authors propose that CHM-monohydroxylated metabolites specific to MDMB-CHMINACA are the most suitable candidates for implementation into bioanalytical assays to demonstrate consumption of this synthetic cannabinoid. Due to the structural similarity of MDMB-CHMINACA and currently trending synthetic cannabinoids whose metabolic profiles have not been reported, the results of this study can be used as a guide to predict their metabolic pathways.