Human cytochrome P450 kinetic studies on six N-2-methoxybenzyl (NBOMe)-derived new psychoactive substances using the substrate depletion approach

Acute, chronic, and post-mortem toxicity: a review focused on three different classes of new psychoactive substances

PURPOSE

New psychoactive substances (NPS) are not controlled under the Single Convention on Narcotic Drugs of 1961 or the 1971 Convention, but they may pose a public health threat. Knowledge of the main properties and toxicological effects of these substances is lacking. According to the current Drugs Law (Law n. 11.343/2006), the Brazilian Surveillance Agency issues directives for forbidden substances in Brazil, and structural classes of synthetic cannabinoids, cathinones, and phenylethylamines are considered illicit drugs. Considering that data on these controlled substances are scattered, the main objective of this work was to collect and organize data to generate relevant information on the toxicological properties of NPS.

METHODS

We carried out a literature review collecting information on the acute, chronic, and post-mortem toxicity of these classes of NSP. We searched info in five scientific databases considering works from 2017 to 2021 and performed a statistical evaluation of the data.

RESULTS

Results have shown a general lack of studies in this field given that many NPS have not had their toxicity evaluated. We observed a significant difference in the volume of data concerning acute and chronic/post-mortem toxicity. Moreover, studies on the adverse effects of polydrug use are scarce.

CONCLUSIONS

More in-depth information about the main threats involving NPS use are needed.

4-EA-NBOMe, an amphetamine derivative, alters glutamatergic synaptic transmission through 5-HT1A receptors on cortical neurons from SpragueDawley rat and pyramidal neurons from C57BL/6 mouse

New psychoactive substances (NPSs) are compounds designed to mimic illegal recreational drugs. In particular, there are difficulties in legal restrictions because there is no fast NPS detection method to suppress the initial spread of NPS with criminal records; thus, they expose the public to serious health threats, including toxicity and dependence. However, the effects of NPSs on the brain and the related cellular mechanisms are well unknown. One of the recently emerging drugs is 4-ethylamphetamine-NBOMe (4-EA-NBOMe), a member of the 2 C phenylalanine family with a similar structure to methamphetamine (methA). In this study, we tested the effect of methA analogs on the glutamatergic synaptic transmission on primary cultured cortical neurons of SpragueDawley (SD) rats and C57BL/6 mice, and also layer 2/3 pyramidal neurons of the medial prefrontal cortex (mPFC) of C57BL/6 mice. We found that acute treatment with 4-EA-NBOMe inhibits spontaneous excitatory postsynaptic currents (EPSCs) and that withdrawal after chronic inhibition by 4-EA-NBOMe augments glutamatergic synaptic transmission. These modifications of synaptic responses are mediated by 5-HT_1A receptors. These findings suggest that 4-EA-NBOMe directly affects the central nervous system by changing the efficacy of glutamatergic synaptic transmission.

Biomedical Research on Substances of Abuse: The Italian Case Study

Substances of abuse have the potential to cause addiction, habituation or altered consciousness. Most of the research on these substances focuses on addiction, and is carried out through observational and clinical studies on humans, or experimental studies on animals. The transposition of the EU Directive 2010/63 into Italian law in 2014 (IT Law 2014/26) includes a ban on the use of animals for research on substances of abuse. Since then, in Italy, public debate has continued on the topic, while the application of the Article prohibiting animal research in this area has been postponed every couple of years. In the light of this debate, we briefly review a range of methodologies - including animal and non-animal, as well as patient or population-based studies - that have been employed to address the biochemical, neurobiological, toxicological, clinical and behavioural effects of substances of abuse and their dependency. We then discuss the implications of the Italian ban on the use of animals for such research, proposing concrete and evidence-based solutions to allow scientists to pursue high-quality basic and translational studies within the boundaries of the regulatory and legislative framework.

An HPLC-UV validated bioanalytical method for measurement of in vitro phase 1 kinetics of α-synuclein binding bifunctional compounds

Aggregates of the protein α-synuclein are associated with pathophysiology of Parkinson's disease and are present in Lewy Bodies found in the brains of Parkinson's patients. We previously demonstrated that bifunctional compounds composed of caffeine linked via a six carbon chain to either 1-aminoindan (C₈-6-I) or nicotine (C₈-6-N) bind α-synuclein and protect yeast cells from α-synuclein mediated toxicity.A critical step in development of positron emission tomography (PET) probes for neurodegenerative diseases is evaluation of their metabolic stability. We determined that C₈-6-I, and C₈-6-N both undergo phase 1 P450 metabolism in mouse, rat, and human liver microsomes. We utilised this metabolic information to guide the design of fluorinated analogues for use as PET probes and determined that the fluorine in ¹⁹F-C₈-6-I and ¹⁹F-C₈-6-N is stable to P450 enzymes.We have developed and validated an analytical HPLC-UV method following FDA and EMA guidelines to measure in vitro phase 1 kinetics of these compounds and determine their V_max, K_M and CL_int,u in mouse liver microsomes. We found that C₈-6-I and ¹⁹F-C₈-6-I have a two- to fourfold lower CL_int,u than C₈-6-N, and ¹⁹F-C₈-6-N. Our approach shows a simple, specific, and effective system to design and develop compounds as PET probes.

Establishment of Neurotoxicity Assessment Using Microelectrode Array (MEA) with hiPSC-Derived Neurons and Evaluation of New Psychoactive Substances (NPS)

Background and Objectives

Currently, safety pharmacological tests for the central nervous system depend on animal behavioral analysis. However, due to the subjectivity of behavioral analysis and differences between species, there is a limit to appropriate nervous system toxicity assessment, therefore a new neurotoxicity assessment that can simulate the human central nervous system is required.

Methods and Results

In our study, we developed an in vitro neurotoxicity assessment focusing on neuronal function. To minimize the differences between species and fast screening, hiPSC-derived neurons and a microelectrode array (MEA) that could simultaneously measure the action potentials of the neuronal networks were used. After analyzing the molecular and electrophysiological characters of our neuronal network, we conducted a neurotoxicity assessment on neurotransmitters, neurotoxicants, illicit drugs, and new psychoactive substances (NPS). We found that most substances used in our experiments responded more sensitively to our MEA-based neurotoxicity assessment than to the conventional neurotoxicity assessment. Also, this is the first paper that evaluates various illicit drugs and NPS using MEA-based neurotoxicity assessment using hiPSC-derived neurons.

Conclusions

Our study expanded the scope of application of neurotoxicity assessment using hiPSC-derived neurons to NPS, and accumulated evaluation data of various toxic substances for hiPSC-derived neurons.

The new psychoactive substances 25H-NBOMe and 25H-NBOH induce abnormal development in the zebrafish embryo and interact in the DNA major groove

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25H-NBOMe and 25H-NBOH recreational drugs induces abnormal formation in zebrafish embryos.

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Biophysical and theoretical studies indicate that these drugs have affinity for the DNA major groove.

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The toxicity observed in the zebrafish embryos and DNA interaction may be correlated.

Toxicological effects of 25H-NBOMe and 25H-NBOH recreational drugs on zebrafish embryos and larvae at the end of 96 h exposure period were demonstrated. 25H-NBOH and 25H-NBOMe caused high embryo mortality at 80 and 100 µg mL⁻¹, respectively. According to the decrease in the concentration tested, lethality decreased while non-lethal effects were predominant up to 10 and 50 µg mL⁻¹ of 25H-NBOH and 25H-NBOMe, respectively, including spine malformation, egg hatching delay, body malformation, otolith malformation, pericardial edema, and blood clotting. We can disclose that these drugs have an affinity for DNA in vitro using biophysical spectroscopic assays and molecular modeling methods. The experiments demonstrated that 25H-NBOH and 25H-NBOMe bind to the unclassical major groove of ctDNA with a binding constant of 27.00 × 10⁴ M⁻¹ and 5.27 × 10⁴ M⁻¹, respectively. Furthermore, these interactions lead to conformational changes in the DNA structure. Therefore, the results observed in the zebrafish embryos and DNA may be correlated.

25CN-NBOMe Metabolites in Rat Urine, Human Liver Microsomes and C.elegans-Structure Determination and Synthesis of the Most Abundant Metabolites

N-Benzylphenethylamines are novel psychedelic substances increasingly used for research, diagnostic, or recreational purposes. To date, only a few metabolism studies have been conducted for N-2-methoxybenzylated compounds (NBOMes). Thus, the available 2,5-dimethoxy-4-(2-((2-methoxybenzyl)amino)ethyl)benzonitrile (25CN-NBOMe) metabolism data are limited. Herein, we investigated the metabolic profile of 25CN-NBOMe in vivo in rats and in vitro in Cunninghamella elegans (C. elegans) mycelium and human liver microsomes. Phase I and phase II metabolites were first detected in an untargeted screening, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) identification of the most abundant metabolites by comparison with in-house synthesized reference materials. The major metabolic pathways described within this study (mono- and bis-O-demethylation, hydroxylation at different positions, and combinations thereof, followed by the glucuronidation, sulfation, and/or N-acetylation of primary metabolites) generally correspond to the results of previously reported metabolism of several other NBOMes. The cyano functional group was either hydrolyzed to the respective amide or carboxylic acid or remained untouched. Differences between species should be taken into account in studies of the metabolism of novel substances.

How to Study the Metabolism of New Psychoactive Substances for the Purpose of Toxicological Screenings-A Follow-Up Study Comparing Pooled Human Liver S9, HepaRG Cells, and Zebrafish Larvae

The new psychoactive substances (NPS) market continues to be very dynamic. A large number of compounds belonging to diverse chemical groups continue to emerge. This makes their detection in biological samples challenging for clinical and forensic toxicologists. Knowledge of the metabolic fate of NPS is crucial for developing comprehensive screening procedures. As human studies are not feasible due to ethical concerns, the current study aimed to compare the NPS' metabolic pattern in incubations with pooled human liver S9 fraction (pHLS9), human liver HepaRG cells, and zebrafish larvae. The latter model was recently shown to be a promising preclinical surrogate for human hepatic metabolism of a synthetic cannabinoid. However, studies concerning other NPS classes are still missing and therefore an amphetamine-based N-methoxybenzyl (NBOMe) compound, a synthetic cathinone, a pyrrolidinophenone analog, a lysergamide, as well as another synthetic cannabinoid were included in the current study. Liquid chromatography coupled to Orbitrap-based high-resolution tandem mass spectrometry was used to analyze metabolic data. Zebrafish larvae were found to produce the highest number of phase I but also phase II metabolites (79 metabolites in total), followed by HepaRG cells (66 metabolites). Incubations with pHLS9 produced the least metabolites (57 metabolites). Furthermore, the involvement of monooxygenases and esterases in the metabolic phase I transformations of 4F-MDMB-BINACA was elucidated using single-enzyme incubations. Several cytochrome P450 (CYP) isozymes were shown to contribute, and CYP3A5 was involved in all CYP-catalyzed reactions, while amide and ester hydrolysis were catalyzed by the human carboxylesterase (hCES) isoforms hCES1b and/or hCES1c. Finally, metabolites were compared to those present in human biosamples if data were available. Overall, the metabolic patterns in HepaRG cells provided the worst overlap with that in human biosamples. Zebrafish larvae experiments agreed best with data found in human plasma and urine analysis. The current study underlines the potential of zebrafish larvae as a tool for elucidating the toxicokinetics of NPS in the future.

NBOMes-Highly Potent and Toxic Alternatives of LSD

Recently, a new class of psychedelic compounds named NBOMe (or 25X-NBOMe) has appeared on the illegal drug market. NBOMes are analogs of the 2C family of phenethylamine drugs, originally synthesized by Alexander Shulgin, that contain a N-(2-methoxy)benzyl substituent. The most frequently reported drugs from this group are 25I-NBOMe, 25B-NBOMe, and 25C-NBOMe. NBOMe compounds are ultrapotent and highly efficacious agonists of serotonin 5-HT_2A and 5-HT_2C receptors (Ki values in low nanomolar range) with more than 1000-fold selectivity for 5-HT_2A compared with 5-HT_1A. They display higher affinity for 5-HT_2A receptors than their 2C counterparts and have markedly lower affinity, potency, and efficacy at the 5-HT_2B receptor compared to 5-HT_2A or 5-HT_2C. The drugs are sold as blotter papers, or in powder, liquid, or tablet form, and they are administered sublingually/buccally, intravenously, via nasal insufflations, or by smoking. Since their introduction in the early 2010s, numerous reports have been published on clinical intoxications and fatalities resulting from the consumption of NBOMe compounds. Commonly observed adverse effects include visual and auditory hallucinations, confusion, anxiety, panic and fear, agitation, uncontrollable violent behavior, seizures, excited delirium, and sympathomimetic signs such mydriasis, tachycardia, hypertension, hyperthermia, and diaphoresis. Rhabdomyolysis, disseminated intravascular coagulation, hypoglycemia, metabolic acidosis, and multiorgan failure were also reported. This survey provides an updated overview of the pharmacological properties, pattern of use, metabolism, and desired effects associated with NBOMe use. Special emphasis is given to cases of non-fatal and lethal intoxication involving these compounds. As the analysis of NBOMes in biological materials can be challenging even for laboratories applying modern sensitive techniques, this paper also presents the analytical methods most commonly used for detection and identification of NBOMes and their metabolites.

DARK Classics in Chemical Neuroscience: NBOMes

N-Benzylphenethylamines, commonly known as NBOMes, are synthetic psychedelic compounds derived from the phenethylamine class of psychedelics (2C-X compounds), which originally have been derived from the naturally occurring alkaloid mescaline. Analogously to their parent compounds and other classical psychedelics, such as psilocybin and lysergic acid diethylamide (LSD), NBOMes are believed to exert their main pharmacological effects through activation of serotonin 2A (5-HT_2A) receptors. Since their introduction as New Psychoactive Substances (NPSs) in 2010, NBOMes have been widely used for recreational purposes; this has resulted in numerous cases of acute toxicity, sometimes with lethal outcomes, leading to the classification of several NBOMes as Schedule I substances in 2013. However, in addition to their recreational use, the NBOMe class has yielded several important biochemical tools, including [¹¹C]Cimbi-36, which is now being used in positron emission tomography (PET) studies of the 5-HT_2A and 5-HT_2C receptors in the mammalian brain, and 25CN-NBOH, one of the most selective 5-HT_2A receptor agonists developed to date. In this Review, the history, chemistry, structure-activity relationships, ADME (absorption, distribution, metabolism, and excretion) properties, and safety profiles of NBOMes will be outlined and discussed.

Human biodistribution and radiation dosimetry of the 5-HT2A receptor agonist Cimbi-36 labeled with carbon-11 in two positions

Background

Cimbi-36 can be ¹¹C-labeled to form an agonist radioligand used for positron emission tomography (PET) imaging of the 5-HT_2A receptor in the brain. In its non-labeled form (25B-NBOMe), it is used as a recreational drug that can lead to severe adverse effects, in some cases, with fatal outcome. We investigated human biodistribution and radiation dosimetry of the radioligand with two different radiolabeling positions. Seven healthy volunteers underwent dynamic 120-min whole-body PET scans (injection of 581 ± 16 MBq, n = 5 for ¹¹C-Cimbi-36; 593 ± 14 MBq, n = 2 for ¹¹C-Cimbi-36_5). Time-integrated activity coefficients (TIACs) from time-activity curves (TACs) of selected organs were used as input into the OLINDA/EXM software to obtain dosimetry information for both ¹¹C-labeling positions of Cimbi-36.

Results

The effective dose was only slightly higher for ¹¹C-Cimbi-36 (5.5 μSv/MBq) than for ¹¹C-Cimbi-36_5 (5.3 μSv/MBq). Standard uptake value (SUV) curves showed higher uptake of ¹¹C-Cimbi-36 in the pancreas, small intestines, liver, kidney, gallbladder, and urinary bladder compared with ¹¹C-Cimbi-36_5, reflecting differences in radiometabolism for the two radioligands. Variability in uptake in excretory organs for ¹¹C-Cimbi-36 points to inter-individual differences with regard to metabolic rate and route. Surprisingly, moderate uptake was found in brown adipose tissue (BAT) in four subjects, possibly representing specific 5-HT_2A/2C receptor binding.

Conclusion

The low effective dose of 5.5 μSv/MBq allows for the injection of up to 1.8 GBq for healthy volunteers per study (equivalent to 3 scans if injecting 600 MBq) and still stay below the international guidelines of 10 mSv, making ¹¹C-Cimbi-36 eligible for studies involving a series of PET scans in a single subject. The biodistribution of Cimbi-36 (and its metabolites) may also help to shed light on the toxic effects of 25B-NBOMe when used in pharmacological doses in recreational settings.

Electronic supplementary material

The online version of this article (10.1186/s13550-019-0527-4) contains supplementary material, which is available to authorized users.

Nano liquid chromatography-high-resolution mass spectrometry for the identification of metabolites of the two new psychoactive substances N-(ortho-methoxybenzyl)-3,4-dimethoxyamphetamine and N-(ortho-methoxybenzyl)-4-methylmethamphetamine

Among the emerging new psychoactive substances (NPS), compounds carrying an N-ortho-methoxybenzyl substituent, the so-called NBOMes, represented a highly potent group of new hallucinogens. Recently, 3,4-dimethoxyamphetamine (3,4-DMA)-NBOMe and 4-methylmethamphetamine (4-MMA)-NBOMe occurred, but no data on their pharmacokinetics were available. According to other NBOMes, they are expected to be extensively metabolized. For detection and identification of their phase I and II metabolites, nano liquid chromatography coupled to high resolution tandem mass spectrometry (nanoLC-HRMS/MS) was used. Rat urine was prepared by simple dilution and incubation mixtures with pooled human liver S9 fraction by precipitation. Furthermore, the results concerning detectability using the new nanoLC approach were compared to those obtained by conventional ultra-high performance LC (UHPLC). In addition, the detectability of the compounds by standard urine screening approaches (SUSAs) routinely used by the authors with UHPLC-HRMS/MS, LC-MSⁿ, and GC-MS was tested. Both NBOMes were extensively metabolized mainly by O-demethylation and conjugation with glucuronic acid (3,4-DMA-NBOMe) or oxidation of the tolyl group to the corresponding carboxylic acid (4-MMA-NBOMe). The developed nanoLC-HRMS/MS approach was successfully applied for identification of 38 3,4-DMA-NBOMe metabolites and 33 4-MMA-NBOMe metabolites confirming its detection power. Furthermore, the solvent saving nanoLC system showed comparable results to the UHPLC-HRMS/MS approach. In addition, an intake of an estimated low common user's dose of the compounds was detectable by all SUSAs only via their metabolites. Suggested targets for urine screening procedures were O-demethyl- and O,O-bis-demethyl-3,4-DMA-NBOMe and their glucuronides and carboxy-4-MMA-NBOMe and its glucuronide and N-demethyl-carboxy-4-MMA-NBOMe.