Metabolite profiling of RCS-4, a novel synthetic cannabinoid designer drug, using human hepatocyte metabolism and TOF-MS

Advances in urinary biomarker research of synthetic cannabinoids

New psychoactive substances (NPS) are chemical compounds designed to mimic the action of existing illicit recreational drugs. Synthetic cannabinoids (SCs) are a subclass of NPS which bind to the cannabinoid receptors, CB1 and CB2, and mimic the action of cannabis. SCs have dominated recent NPS seizure reports worldwide. While urine is the most common matrix for drug-of-abuse testing, SCs undergo extensive Phase I and Phase II metabolism, resulting in almost undetectable parent compounds in urine samples. Therefore, the major urinary metabolites of SCs are usually investigated as surrogate biomarkers to identify their consumption. Since seized urine samples after consuming novel SCs may be unavailable in a timely manner, human hepatocytes, human liver microsomes and human transporter overexpressed cell lines are physiologically-relevant in vitro systems for performing metabolite identification, metabolic stability, reaction phenotyping and transporter experiments to establish the disposition of SC and its metabolites. Coupling these in vitro experiments with in vivo verification using limited authentic urine samples, such a two-pronged approach has proven to be effective in establishing urinary metabolites as biomarkers for rapidly emerging SCs.

Cannabinoids: Recent Updates on Public Perception, Adverse Reactions, Pharmacokinetics, Pretreatment Methods and Their Analysis Methods

Cannabinoids (CBDs) have been traditionally used as a folk medicine. Recently, they have been found to exhibit a high pharmacological potential. However, they are addicted and are often abused by drug users, thereby, becoming a threat to public safety. CBDs and their metabolites are usually found in trace levels in plants or in biological matrices and, are therefore not easy to be detected. Advances have been made toward accurately analyzing CBDs in plants or in biological matrices. This review aims at elucidating on the consumption of CBDs as well as its adverse effects and to provide a comprehensive overview of CBD pretreatment and detection methods. Moreover, novel pretreatment methods such as microextraction, Quick Easy Cheap Effective Rugged Safe and online technology as well as novel analytic methods such as ion-mobility mass spectrometry, application of high resolution mass spectrometry in nontarget screening are summarized. In addition, we discuss and compare the strengths and weaknesses of different methods and suggest their future prospect.

Distribution of Synthetic Cannabinoids JWH-210, RCS-4 and Δ 9-Tetrahydrocannabinol After Intravenous Administration to Pigs

Background:

Synthetic cannabinoids (SCs) have become an increasing issue in forensic toxicology. Controlled human studies evaluating pharmacokinetic data of SCs are lacking and only few animal studies have been published. Thus, an interpretation of analytical results found in intoxicated or poisoned individuals is difficult. Therefore, the distribution of two selected SCs, namely 4-ethylnaphthalen-1-yl-(1-pentylindol-3-yl)methanone (JWH-210) and 2-(4-methoxyphenyl)-1-(1-pentyl-indol-3-yl)methanone (RCS-4) as well as ∆9-tetrahydrocannabinol (THC) as reference were examined in pigs.

Methods:

Pigs (n = 6 per drug) received a single intravenous 200 µg/kg BW dose of JWH-210, RCS-4, or THC. Six hours after administration, the animals were exsanguinated and relevant organs, important body fluids such as bile, and tissues such as muscle and adipose tissue, as well as the bradytrophic specimens dura and vitreous humor were collected. After hydrolysis and solid phase extraction, analysis was performed by LC-MS/MS. To overcome matrix effects of the LC-MS/MS analysis, a standard addition method was applied for quantification.

Results:

The parent compounds could be detected in every analyzed specimen with the exception of THC that was not present in dura and vitreous humor. Moderate concentrations were present in brain, the site of biological effect. Metabolite concentrations were highest in tissues involved in metabolism and/or elimination.

Conclusions:

Besides kidneys and lungs routinely analyzed in postmortem toxicology, brain, adipose, and muscle tissue could serve as alternative sources, particularly if other specimens are not available. Bile fluid is the most appropriate specimen for SCs and THC metabolites detection.

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

Metabolite profiling of novel psychoactive substances (NPS) is critical for documenting drug consumption. N-(1-amino-3,3-dimethyl-1-oxobutan-2-yl)-1-(4-fluorobenzyl)-1H-indazole-3-carboxamide (ADB-FUBINACA) is an emerging synthetic cannabinoid whose toxicological and metabolic data are currently unavailable. We aimed to determine optimal markers for identifying ADB-FUBINACA intake. Metabolic stability was evaluated with human liver microsome incubations. Metabolites were identified after 1 and 3 h incubation with pooled human hepatocytes, liquid chromatography- high resolution mass spectrometry in positive-ion mode (5600+ TripleTOF®, Sciex) and several data mining approaches (MetabolitePilot™, Sciex). Metabolite separation was achieved on an Ultra Biphenyl column (Restek®); full-scan TOF-MS and information-dependent acquisition MS/MS data were acquired. ADB-FUBINACA microsomal half-life was 39.7 min, with a predicted hepatic clearance of 9.0 mL/min/kg and a 0.5 extraction ratio (intermediate-clearance drug). Twenty-three metabolites were identified. Major metabolic pathways were alkyl and indazole hydroxylation, terminal amide hydrolysis, subsequent glucuronide conjugations, and dehydrogenation. We recommend ADB-FUBINACA hydroxyalkyl, hydroxydehydroalkyl and hydroxylindazole metabolites as ADB-FUBINACA intake markers. N-dealkylated metabolites are not specific ADB-FUBINACA metabolites and should not be used as definitive markers of consumption. This is the first ADB-FUBINACA in vitro metabolism study; in vivo experiments enabling pharmacokinetic and pharmacodynamics studies or urine from authentic clinical/forensic cases are needed to confirm our results.

Distinguishing Intake of New Synthetic Cannabinoids ADB-PINACA and 5F-ADB-PINACA with Human Hepatocyte Metabolites and High-Resolution Mass Spectrometry

BACKGROUND

ADB-PINACA and its 5-fluoropentyl analog 5F-ADB-PINACA are among the most potent synthetic cannabinoids tested to date, with several severe intoxication cases. ADB-PINACA and 5F-ADB-PINACA have a different legal status, depending on the country. Synthetic cannabinoid metabolites predominate in urine, making detection of specific metabolites the most reliable way for proving intake in clinical and forensic specimens. However, there are currently no data on ADB-PINACA and 5F-PINACA metabolism. The substitution of a single fluorine atom distinguishes the 2 molecules, which may share common major metabolites. For some legal applications, distinguishing between ADB-PINACA and 5F-PINACA intake is critical. For this reason, we determined the human metabolic fate of the 2 analogs.

METHODS

ADB-PINACA and 5F-PINACA were incubated for 3 h with pooled cryopreserved human hepatocytes, followed by liquid chromatography—high-resolution mass spectrometry analysis. Data were processed with Compound Discoverer.

RESULTS

We identified 19 and 12 major ADB-PINACA and 5F-ADB-PINACA metabolites, respectively. Major metabolic reactions included pentyl hydroxylation, hydroxylation followed by oxidation (ketone formation), and glucuronidation of ADB-PINACA, and oxidative defluorination followed by carboxylation of 5F-ADB-PINACA.

CONCLUSIONS

We recommend ADB-PINACA ketopentyl and hydroxypentyl, and ADB-PINACA 5-hydroxypentyl and pentanoic acid, as optimal markers for ADB-PINACA and 5F-ADB-PINACA intake, respectively. Since the 2 compounds present positional isomers as the primary metabolites, monitoring unique product ions and optimized chromatographic conditions are required for a clear distinction between ADB-PINACA and 5F-ADB-PINACA intake.

High-resolution mass spectrometry in toxicology: current status and future perspectives

This paper reviews high-resolution mass spectrometry (HRMS) approaches using time-of-flight or Orbitrap techniques for research and application in various toxicology fields, particularly in clinical toxicology and forensic toxicology published since 2013 and referenced in PubMed. In the introduction, an overview on applications of HRMS in various toxicology fields is given with reference to current review articles. Papers concerning HRMS in metabolism, screening, and quantification of pharmaceuticals, drugs of abuse, and toxins in human body samples are critically reviewed. Finally, a discussion on advantages as well as limitations and future perspectives of these methods is included.

Metabolism and bioactivation of the tricyclic antidepressant amitriptyline in human liver microsomes and human urine

Aim: Amitriptyline is a widely used tricyclic antidepressant, but the metabolic studies were conducted almost 20 years ago using high-performance liquid chromatography coupled with ultraviolet detector or radiolabeled methods. Results: First, multiple ion monitoring (MIM)- enhanced product ion (EPI) scan was used to obtain the diagnostic ions or neutral losses in human liver microsome incubations with amitriptyline. Subsequently, predicted multiple reaction monitoring (MRM)-EPI scan was used to identify the metabolites in human urine with the diagnostic ions or neutral losses. Finally, product ion filtering and neutral loss filtering were used as the data mining tools to screen metabolites. Consequently, a total of 28 metabolites were identified in human urine after an oral administration using LC–MS/MS. Conclusion: An integrated workflow using LC–MS/MS was developed to comprehensively profile the metabolites of amitriptyline in human urine, in which five N-acetyl-l-cysteine conjugates were characterized as tentative biomarkers for idiosyncratic toxicity.

Toxicokinetics of new psychoactive substances: plasma protein binding, metabolic stability, and human phase I metabolism of the synthetic cannabinoid WIN 55,212-2 studied using in vitro tools and LC-HR-MS/MS

The new psychoactive substance WIN 55,212-2 ((R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo-[1,2,3-de]-1,4-benzoxazin-6-yl]-1-napthalenylmethanone) is a potent synthetic cannabinoid receptor agonist. The metabolism of WIN 55,212-2 in man has never been reported. Therefore, the aim of this study was to identify the human in vitro metabolites of WIN 55,212-2 using pooled human liver microsomes and liquid chromatography-high resolution-tandem mass spectrometry (LC-HR-MS/MS) to provide targets for toxicological, doping, and environmental screening procedures. Moreover, a metabolic stability study in pooled human liver microsomes (pHLM) was carried out. In total, 19 metabolites were identified and the following partly overlapping metabolic steps were deduced: degradation of the morpholine ring via hydroxylation, N- and O-dealkylation, and oxidative deamination, hydroxylations on either the naphthalene or morpholine ring or the alkyl spacer with subsequent oxidation, epoxide formation with subsequent hydrolysis, or combinations. In conclusion, WIN 55,212-2 was extensively metabolized in human liver microsomes incubations and the calculated hepatic clearance was comparably high, indicating a fast and nearly complete metabolism in vivo. This is in line with previous findings on other synthetic cannabinoids. Copyright © 2016 John Wiley & Sons, Ltd.

Identification of AKB-48 and 5F-AKB-48 Metabolites in Authentic Human Urine Samples Using Human Liver Microsomes and Time of Flight Mass Spectrometry

The occurrence of structurally related synthetic cannabinoids makes the identification of unique markers of drug intake particularly challenging. The aim of this study was to identify unique and abundant metabolites of AKB-48 and 5F-AKB-48 for toxicological screening in urine. Investigations of authentic urine samples from forensic cases in combination with human liver microsome (HLM) experiments were used for identification of metabolites. HLM incubations of AKB-48 and 5F-AKB-48 along with 35 urine samples from authentic cases were analyzed with liquid chromatography quadrupole tandem time of flight mass spectrometry. Using HLMs 41 metabolites of AKB-48 and 37 metabolites of 5F-AKB-48 were identified, principally represented by hydroxylation but also ketone formation and dealkylation. Monohydroxylated metabolites were replaced by di- and trihydroxylated metabolites within 30 min. The metabolites from the HLM incubations accounted for on average 84% (range, 67-100) and 91% (range, 71-100) of the combined area in the case samples for AKB-48 and 5F-AKB-48, respectively. While defluorinated metabolites accounted for on average 74% of the combined area after a 5F-AKB-48 intake only a few identified metabolites were shared between AKB-48 and 5F-AKB-48, illustrating the need for a systematic approach to identify unique metabolites. HLMs in combination with case samples seem suitable for this purpose.

Pentylindole/Pentylindazole Synthetic Cannabinoids and Their 5-Fluoro Analogs Produce Different Primary Metabolites: Metabolite Profiling for AB-PINACA and 5F-AB-PINACA

Whereas non-fluoropentylindole/indazole synthetic cannabinoids appear to be metabolized preferably at the pentyl chain though without clear preference for one specific position, their 5-fluoro analogs' major metabolites usually are 5-hydroxypentyl and pentanoic acid metabolites. We determined metabolic stability and metabolites of N-(1-amino-3-methyl-1-oxobutan-2-yl)-1-pentyl-1H-indazole-3-carboxamide (AB-PINACA) and 5-fluoro-AB-PINACA (5F-AB-PINACA), two new synthetic cannabinoids, and investigated if results were similar. In silico prediction was performed with MetaSite (Molecular Discovery). For metabolic stability, 1 μmol/L of each compound was incubated with human liver microsomes for up to 1 h, and for metabolite profiling, 10 μmol/L was incubated with pooled human hepatocytes for up to 3 h. Also, authentic urine specimens from AB-PINACA cases were hydrolyzed and extracted. All samples were analyzed by liquid chromatography high-resolution mass spectrometry on a TripleTOF 5600+ (AB SCIEX) with gradient elution (0.1% formic acid in water and acetonitrile). High-resolution full-scan mass spectrometry (MS) and information-dependent acquisition MS/MS data were analyzed with MetabolitePilot (AB SCIEX) using different data processing algorithms. Both drugs had intermediate clearance. We identified 23 AB-PINACA metabolites, generated by carboxamide hydrolysis, hydroxylation, ketone formation, carboxylation, epoxide formation with subsequent hydrolysis, or reaction combinations. We identified 18 5F-AB-PINACA metabolites, generated by the same biotransformations and oxidative defluorination producing 5-hydroxypentyl and pentanoic acid metabolites shared with AB-PINACA. Authentic urine specimens documented presence of these metabolites. AB-PINACA and 5F-AB-PINACA produced suggested metabolite patterns. AB-PINACA was predominantly hydrolyzed to AB-PINACA carboxylic acid, carbonyl-AB-PINACA, and hydroxypentyl AB-PINACA, likely in 4-position. The most intense 5F-AB-PINACA metabolites were AB-PINACA pentanoic acid and 5-hydroxypentyl-AB-PINACA.

Synthetic cannabinoids pharmacokinetics and detection methods in biological matrices

Synthetic cannabinoids (SC), originally developed as research tools, are now highly abused novel psychoactive substances. We present a comprehensive systematic review covering in vivo and in vitro animal and human pharmacokinetics and analytical methods for identifying SC and their metabolites in biological matrices. Of two main phases of SC research, the first investigated therapeutic applications, and the second abuse-related issues. Administration studies showed high lipophilicity and distribution into brain and fat tissue. Metabolite profiling studies, mostly with human liver microsomes and human hepatocytes, structurally elucidated metabolites and identified suitable SC markers. In general, SC underwent hydroxylation at various molecular sites, defluorination of fluorinated analogs and phase II metabolites were almost exclusively glucuronides. Analytical methods are critical for documenting intake, with different strategies applied to adequately address the continuous emergence of new compounds. Immunoassays have different cross-reactivities for different SC classes, but cannot keep pace with changing analyte targets. Gas chromatography and liquid chromatography mass spectrometry assays - first for a few, then numerous analytes - are available but constrained by reference standard availability, and must be continuously updated and revalidated. In blood and oral fluid, parent compounds are frequently present, albeit in low concentrations; for urinary detection, metabolites must be identified and interpretation is complex due to shared metabolic pathways. A new approach is non-targeted HRMS screening that is more flexible and permits retrospective data analysis. We suggest that streamlined assessment of new SC's pharmacokinetics and advanced HRMS screening provide a promising strategy to maintain relevant assays.