The psychoactive aminoalkylbenzofuran derivatives, 5-APB and 6-APB, mimic the effects of 3,4-methylenedioxyamphetamine (MDA) on monoamine transmission in male rats

Locomotor and discriminative stimulus effects of three benzofuran compounds in comparison to abused psychostimulants

Aims

Benzofurans are used recreationally, due their ability to cause psychostimulant and/or entactogenic effects, but unfortunately produce substantial adverse effects, including death. Three benzofurans 5-(2-aminopropyl)-2,3-dihydrobenzofuran (5-APDB), 5-(2-aminopropyl)-2,3-dihydrobenzofuran (5-MAPB) and 6-(2-aminopropyl) benzofuran (6-APB) were tested to determine their behavioral effects in comparison with 2,3-methylenedioxymethamphetamine (MDMA), cocaine, and methamphetamine.

Methods

Locomotor activity was tested in groups of 8 male Swiss-Webster mice in an open-field task to screen for locomotor stimulant or depressant effects and to identify behaviorally active doses and times of peak effect. Discriminative stimulus effects were tested in groups of 6 male Sprague-Dawley rats trained to discriminate MDMA (1.5 mg/kg), cocaine (10 mg/kg), or methamphetamine (1 mg/kg) from saline using a FR 10 for food in a two-lever operant task.

Results

In the locomotor activity test, MDMA (ED50 = 8.34 mg/kg) produced peak stimulant effects 60 to 80 min following injection. 5-MAPB (ED50 = 0.92 mg/kg) produced modest stimulant effects 50 to 80 min after injection, whereas 6-APB (ED50 = 1.96 mg/kg) produced a robust stimulant effect 20 to 50 min after injection. 5-APDB produced an early depressant phase (ED50 = 3.38 mg/kg) followed by a modest stimulant phase (ED50 = 2.57 mg/kg) 20 to 50 min after injection. In the drug discrimination tests, 5-APDB (ED50 = 1.02 mg/kg), 5-MAPB (ED50 = 1.00 mg/kg) and 6-APB (ED50 = 0.32 mg/kg) fully substituted in MDMA-trained rats, whereas only 5-MAPB fully substituted for cocaine, and no compounds fully substituted for methamphetamine.

Conclusions

The synthetic benzofuran compound 5-APDB and 5-MAPB produced weak locomotor effects, whereas 6-APB produced robust locomotor stimulant effects. All compounds were more potent than MDMA. All three compounds fully substituted in MDMA-trained rats suggesting similar subjective effects. Taken together, these results suggest that these benzofuran compounds may have abuse liability as substitutes for MDMA.

Experimental strategies to discover and develop the next generation of psychedelics and entactogens as medicines

Research on classical psychedelics (psilocybin, LSD and DMT) and entactogen, MDMA, has produced a renaissance in the search for more effective drugs to treat psychiatric, neurological and various peripheral disorders. Psychedelics and entactogens act though interaction with 5-HT_2A and other serotonergic receptors and/or monoamine reuptake transporters. 5-HT, which serves as a neurotransmitter and hormone, is ubiquitously distributed in the brain and peripheral organs, tissues and cells where it has vasoconstrictor, pro-inflammatory and pro-nociceptive actions. Serotonergic psychedelics and entactogens have known safety and toxicity risks. For these drugs, the risks been extensively researched and empirically assessed through human experience. However, novel drug-candidates require thorough non-clinical testing not only to predict clinical efficacy, but also to address the risks they pose during clinical development and later after approval as prescription medicines. We have defined the challenges researchers will encounter when developing novel serotonergic psychedelics and entactogens. We describe screening techniques to predict clinical efficacy and address the safety/toxicity risks emerging from our knowledge of the existing drugs: 1) An early-stage, non-clinical screening cascade to pharmacologically characterise novel drug-candidates. 2) Models to detect hallucinogenic activity. 3) Models to differentiate hallucinogens from entactogens. 4) Non-clinical preclinical lead optimisation technology (PLOT) screening to select drug-candidates. 5) Modified animal models to evaluate the abuse and dependence risks of novel psychedelics in Safety Pharmacology testing. Our intention has been to design non-clinical screening strategies that will reset the balance between benefits and harms to deliver more effective and safer novel psychedelics for clinical use. This article is part of the Special Issue on 'National Institutes of Health Psilocybin Research Speaker Series'.

(2-Aminopropyl)benzo[β]thiophenes (APBTs) are novel monoamine transporter ligands that lack stimulant effects but display psychedelic-like activity in mice

Derivatives of (2-aminopropyl)indole (API) and (2-aminopropyl)benzofuran (APB) are new psychoactive substances which produce stimulant effects in vivo. (2-Aminopropyl)benzo[β]thiophene (APBT) is a novel sulfur-based analog of API and APB that has not been pharmacologically characterized. In the current study, we assessed the pharmacological effects of six APBT positional isomers in vitro, and three of these isomers (3-APBT, 5-APBT, and 6-APBT) were subjected to further investigations in vivo. Uptake inhibition and efflux assays in human transporter-transfected HEK293 cells and in rat brain synaptosomes revealed that APBTs inhibit monoamine reuptake and induce transporter-mediated substrate release. Despite being nonselective transporter releasers like MDMA, the APBT compounds failed to produce locomotor stimulation in C57BL/6J mice. Interestingly, 3-APBT, 5-APBT, and 6-APBT were full agonists at 5-HT2 receptor subtypes as determined by calcium mobilization assays and induced the head-twitch response in C57BL/6J mice, suggesting psychedelic-like activity. Compared to their APB counterparts, ABPT compounds demonstrated that replacing the oxygen atom with sulfur results in enhanced releasing potency at the serotonin transporter and more potent and efficacious activity at 5-HT2 receptors, which fundamentally changed the in vitro and in vivo profile of APBT isomers in the present studies. Overall, our data suggest that APBT isomers may exhibit psychedelic and/or entactogenic effects in humans, with minimal psychomotor stimulation. Whether this unique pharmacological profile of APBT isomers translates into potential therapeutic potential, for instance as candidates for drug-assisted psychotherapy, warrants further investigation.

Molecular and clinical aspects of potential neurotoxicity induced by new psychoactive stimulants and psychedelics

New psychoactive stimulants and psychedelics continue to play an important role on the illicit new psychoactive substance (NPS) market. Designer stimulants and psychedelics both affect monoaminergic systems, although by different mechanisms. Stimulant NPS primarily interact with monoamine transporters, either as inhibitors or as substrates. Psychedelic NPS most potently interact with serotonergic receptors and mediate their mind-altering effects mainly through agonism at serotonin 5-hydroxytryptamine-2A (5-HT_2A) receptors. Rarely, designer stimulants and psychedelics are associated with potentially severe adverse effects. However, due to the high number of emerging NPS, it is not possible to investigate the toxicity of each individual substance in detail. The brain is an organ particularly sensitive to substance-induced toxicity due to its high metabolic activity. In fact, stimulant and psychedelic NPS have been linked to neurological and cognitive impairments. Furthermore, studies using in vitro cell models or rodents indicate a variety of mechanisms that could potentially lead to neurotoxic damage in NPS users. Cytotoxicity, mitochondrial dysfunction, and oxidative stress may potentially contribute to neurotoxicity of stimulant NPS in addition to altered neurochemistry. Serotonin 5-HT_2A receptor-mediated toxicity, oxidative stress, and activation of mitochondrial apoptosis pathways could contribute to neurotoxicity of some psychedelic NPS. However, it remains unclear how well the current preclinical data of NPS-induced neurotoxicity translate to humans.

α-PPP and its derivatives are selective partial releasers at the human norepinephrine transporter: A pharmacological characterization of interactions between pyrrolidinopropiophenones and high and low affinity monoamine transporters

While classical cathinones, such as methcathinone, have been shown to be monoamine releasing agents at human monoamine transporters, the subgroup of α-pyrrolidinophenones has thus far solely been characterized as monoamine transporter reuptake inhibitors. Herein, we report data from previously undescribed α-pyrrolidinopropiophenone (α-PPP) derivatives and compare them with the pharmacologically well-researched α-PVP (α-pyrrolidinovalerophenone). Radiotracer-based in vitro uptake inhibition assays in HEK293 cells show that the investigated α-PPP derivatives inhibit the human high-affinity transporters of dopamine (hDAT) and norepinephrine (hNET) in the low micromolar range, with α-PVP being ten times more potent. Similar to α-PVP, no relevant pharmacological activity was found at the human serotonin transporter (hSERT). Unexpectedly, radiotracer-based in vitro release assays reveal α-PPP, MDPPP and 3Br-PPP, but not α-PVP, to be partial releasing agents at hNET (EC50 values in the low micromolar range). Furthermore, uptake inhibition assays at low-affinity monoamine transporters, i.e., the human organic cation transporters (hOCT) 1-3 and human plasma membrane monoamine transporter (hPMAT), bring to light that all compounds inhibit hOCT1 and 2 (IC50 values in the low micromolar range) while less potently interacting with hPMAT and hOCT3. In conclusion, this study describes (i) three new hybrid compounds that efficaciously block hDAT while being partial releasers at hNET, and (ii) highlights the interactions of α-PPP-derivatives with low-affinity monoamine transporters, giving impetus to further studies investigating the interaction of drugs of abuse with OCT1-3 and PMAT.

Domino C–C/C–O bond formation: palladium-catalyzed regioselective synthesis of 7-iodobenzo[b]furans using 1,2,3-triiodobenzenes and benzylketones

A facile and efficient synthesis of 7-iodobenzo[b]furan derivatives via a highly regioselective tandem α-arylation/intramolecular O-arylation of 5-substituted-1,2,3-triiodobenzenes and benzylketones is described. Remarkably, the α-arylation coupling reactions initiate exclusively at the least sterically-hindered position of the triiodoarene, which results in a highly chemoselective transformation. The highest yields were observed in reactions between electron-poor 1,2,3-triiodoarenes and electron-rich benzylketones, yet the optimized reaction conditions were found to be tolerant to a wide range of different functional groups. This unprecedent synthesis of 7-iodobenzo[b]furans from 1,2,3-triiodobenzenes is scalable, general in scope, and provides easy access to valuable precursors for other chemical transformations.

A facile and unprecedented synthesis of 7-iodobenzo[b]furans via a highly regioselective tandem α-arylation/intramolecular O-arylation is reported that is efficient, scalable and creates versatile precursors for further chemical manipulation.

Pharmacotherapy of Patients Taking New Psychoactive Substances: A Systematic Review and Analysis of Case Reports

Background: In recent years, an increase in the frequency of hospitalizations of patients taking newer and newer psychoactive substances has been observed around the world. Each year, authors publish case reports of patients who consumed previously unknown NPS. Most publications of this type concern the period between 2014 and 2016. However, no publication systematically reviews the pharmacotherapy used in these cases. This study aims to review the case reports of patients taking NPS published between 2010 and 2019, as well as analyzing the pharmacotherapy used. Methods: We searched the Thomson (Web of Knowledge), PubMed/Medline, Science Direct, Scopus and Google Scholar databases. The search was performed using all possible combinations of the term "case report" describing the use of NPS, also referred to as designer medications, internet medications, research chemicals and herbal highs. Results: We analyzed 51 case reports on the intake of various types of NPS. Most of them (p < 0.001) concerned the use of synthetic cannabinoids (41.2%) and cathinones (31.4%). The pharmacotherapy applied primarily (p < 0.001) consisted of administering benzodiazepines to patients (62.7%), most of whom took only this group of medications (25.5%), followed by groups receiving benzodiazepines combined with neuroleptics (15.7%) and muscle relaxants (11.8%). Opioids were administered primarily to patients taking synthetic opioids (p < 0.001). Of the 5 cases of deaths from NPS reported in the literature, three relate specifically to the synthetic opioid MT-45. The later the time period, the more medications patients were administered (p = 0.02). Conclusion: In the pharmacotherapy for NPS poisoning, one should focus primarily on combating psychomotor agitation.