Indol-3-ylcycloalkyl Ketones: Effects of N1 Substituted Indole Side Chain Variations on CB2 Cannabinoid Receptor Activity

Unlocking Enantioselectivity: Synergy of 2-Pyridone and Chiral Amino Acids in Pd-Catalyzed β-C(sp3)-H Transformations

Enantioselective C(sp3)-H activation has garnered significant attention in synthetic and computational chemistry. Chiral transient directing groups (TDGs) hold promise for enabling Pd(II)-catalyzed enantioselective C(sp3)-H functionalization. Despite the interest in this strategy, it presents a challenge because the stereogenic center on the chiral TDG is frequently distant from the C-H bond, leading to a mixture of functionalized products. Our computational study on Pd(II)-catalyzed enantioselective β-C(sp3)-H arylation of aliphatic ketone with chiral amino acids provides a sustainable route to synthesizing complex chiral molecular scaffolds. The cooperative action of 2-pyridone derivatives and chiral amino acids is crucial in promoting the enantio-discriminating C-H activation, oxidative addition, and reductive elimination steps. Using 5-nitro-2-pyridone as the optimal external ligand demonstrates its ability to achieve the highest level of enantioselection. In contrast, the modeled 3,5-di((trifluoromethyl)sulfonyl)-2-pyridone ligand facilitates the most straightforward C-H activation. This study underscores the pivotal role of the alkyl substituent at the α-position of the amino acid (TDG) in altering enantioselectivity.

A highly potent, orally bioavailable pyrazole-derived cannabinoid CB2 receptor-selective full agonist for in vivo studies

The cannabinoid CB2 receptor (CB2R) is a potential therapeutic target for distinct forms of tissue injury and inflammatory diseases. To thoroughly investigate the role of CB2R in pathophysiological conditions and for target validation in vivo , optimal pharmacological tool compounds are essential. Despite the sizable progress in the generation of potent and selective CB2R ligands, pharmacokinetic parameters are often neglected for in vivo studies. Here, we report the generation and characterization of a tetra-substituted pyrazole CB2R full agonist named RNB-61 with high potency ( K i 0.13-1.81 nM, depending on species) and a peripherally restricted action due to P-glycoprotein mediated efflux from the brain. 3 H and 14 C labelled RNB-61 showed apparent K d values < 4 nM towards human CB2R in both cell and tissue experiments. The >6000-fold selectivity over CB1 receptors and negligible off-targets in vitro , combined with high oral bioavailability and suitable systemic pharmacokinetic (PK) properties, prompted the assessment of RNB-61 in a mouse ischemia-reperfusion model of acute kidney injury (AKI) and in a rat model of chronic kidney injury/inflammation and fibrosis (CKI) induced by unilateral ureteral obstruction. RNB-61 exerted dose-dependent nephroprotective and/or antifibrotic effects in the AKI/CKI models. Thus, RNB-61 is an optimal CB2R tool compound for preclinical in vivo studies with superior biophysical and PK properties over generally used CB2R ligands.

Cannabinoids: Emerging sleep modulator

Sleep is an essential biological phase of our daily life cycle and is necessary for maintaining homeostasis, alertness, metabolism, cognition, and other key functions across the animal kingdom. Dysfunctional sleep leads to deleterious effects on health, mood, and cognition, including memory deficits and an increased risk of diabetes, stroke, and neurological disorders. Sleep is regulated by several brain neuronal circuits, neuromodulators, and neurotransmitters, where cannabinoids have been increasingly found to play a part in its modulation. Cannabinoids, a group of lipid metabolites, are regulatory molecules that bind mainly to cannabinoid receptors (CB1 and CB2). Much evidence supports the role of cannabinoid receptors in the modulation of sleep, where their alteration exhibits sleep-promoting effects, including an increase in non-rapid-eye movement sleep and a reduction in sleep latency. However, the pharmacological alteration of CB1 receptors is associated with adverse psychotropic effects, which are not exhibited in CB2 receptor alteration. Hence, selective alteration of CB2 receptors is also of clinical importance, where it could potentially be used in treating sleep disorders. Thus, it is crucial to understand the neurobiological basis of cannabinoids in sleep physiology. In this review article, the alteration of the endocannabinoid system by various cannabinoids and their respective effects on the sleep-wake cycle are discussed based on recent findings. The mechanisms of the cannabinoid receptors on sleep and wakefulness are also explored for their clinical implications and potential therapeutic use on sleep disorders.

Systematic Modification of the Substitution Pattern of the 7-Hydroxy-5-oxopyrazolo[4,3-b]pyridine-6-carboxamide Scaffold Enabled the Discovery of New Ligands with High Affinity and Selectivity for the Cannabinoid Type 2 Receptor

Selective ligands of the CB2 receptor are receiving considerable attention due to their potential as therapeutic agents for a variety of diseases. Recently, 7-hydroxy-5-oxopyrazolo[4,3-b]pyridine-6-carboxamide derivatives were shown to act at the CB2 receptor either as agonists or as inverse agonists/antagonists in vitro and to have anti-osteoarthritic activity in vivo. In this article, we report the synthesis, pharmacological profile, and molecular modeling of a series of twenty-three new 7-hydroxy-5-oxopyrazolo[4,3-b]pyridine-6-carboxamides with the aim of further developing this new class of selective CB2 ligands. In addition to these compounds, seven other analogs that had been previously synthesized were included in this study to better define the structure-activity relationship (SAR). Ten of the new compounds studied were found to be potent and selective ligands of the CB2 receptor, with K_i values ranging from 48.46 to 0.45 nM and CB1/CB2 selectivity indices (SI) ranging from >206 to >4739. In particular, compounds 54 and 55 were found to be high-affinity CB2 inverse agonists that were not active at all at the CB1 receptor, whereas 57 acted as an agonist. The functional activity profile of the compounds within this structural class depends mainly on the substitution pattern of the pyrazole ring.

Design, synthesis, and evaluation of substituted alkylindoles that activate G protein-coupled receptors distinct from the cannabinoid CB1 and CB2 receptors

The alkylindole (AI), WIN55212-2, modulates the activity of several proteins, including cannabinoid receptors 1 and 2 (CB1R, CB2R), and at least additional G protein-coupled receptor (GPCR) that remains uncharacterized with respect to its molecular identity and pharmacological profile. Evidence suggests that such AI-sensitive GPCRs are expressed by the human kidney cell line HEK293. We synthesized fourteen novel AI analogues and evaluated their activities at AI-sensitive GPCRs using [35S]GTPγS and [3H]WIN55212-2 binding in HEK293 cell membranes, and performed in silico pharmacophore modeling to identify characteristics that favor binding to AI-sensitive GPCRs versus CB1R/CB2R. Compounds 10 and 12 stimulated [35S]GTPγS binding (EC50s = 3.5 and 1.1 nM, respectively), and this response was pertussis toxin-sensitive, indicating that AI-sensitive GPCRs couple to Gi/o proteins. Five AI analogues reliably distinguished two binding sites that correspond to the high and low affinity state of AI-sensitive GPCRs coupled or not to G proteins. In silico pharmacophore modeling suggest 3 characteristics that favor binding to AI-sensitive GPCRs versus CB1R/CB2R: 1) an s-cis orientation of the two aromatic rings in AI analogues, 2) a narrow dihedral angle between the carbonyl group and the indole ring plane [i.e., O-C(carbonyl)-C3-C2] and 3) the presence of a carbonyl oxygen. The substituted alkylindoles reported here represent novel chemical tools to study AI-sensitive GPCRs.

EMCDDA framework and practical guidance for naming synthetic cannabinoids

Synthetic cannabinoids (SCs), often sold as "legal" replacements for cannabis, are the largest group of new psychoactive substances monitored by the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA). Currently, close to 240 structurally heterogeneous SCs are monitored through the European Union (EU) Early Warning System, and attributing consistent, informative, and user-friendly names to SCs has been a challenge in the past. Over time, several naming conventions have been employed with the aim of making SCs more easily recognizable by non-chemists, including regulators. To achieve this, the names assigned need to contain detailed information on the structural features present in the substance. This work provides a theoretical framework and a practical hands-on guideline for consistent naming of SCs, which is easy to understand and can be applied by the forensic community, researchers, clinical practitioners, and policy-makers. The proposed framework builds on the established letter code system for molecular building blocks (core, linker, linked group, and tail) implemented by the EMCDDA in 2013 and has been expanded to incorporate additional structural features through substitution. The scope of the issue of attributing semi-systematic code names is illustrated, and earlier approaches used for naming SCs are discussed. The concepts and rules of the EMCDDA framework are described through a flowchart that provides a basis for naming new SCs, a graphical overview of the chemical diversity of SCs, and a detailed list of the SCs identified in the EU by the Early Warning System of the EMCDDA for reference.

Why Do Marijuana and Synthetic Cannabimimetics Induce Acute Myocardial Infarction in Healthy Young People?

The use of cannabis preparations has steadily increased. Although cannabis was traditionally assumed to only have mild vegetative side effects, it has become evident in recent years that severe cardiovascular complications can occur. Cannabis use has recently even been added to the risk factors for myocardial infarction. This review is dedicated to pathogenetic factors contributing to cannabis-related myocardial infarction. Tachycardia is highly important in this respect, and we provide evidence that activation of CB₁ receptors in brain regions important for cardiovascular regulation and of presynaptic CB₁ receptors on sympathetic and/or parasympathetic nerve fibers are involved. The prototypical factors for myocardial infarction, i.e., thrombus formation and coronary constriction, have also been considered, but there is little evidence that they play a decisive role. On the other hand, an increase in the formation of carboxyhemoglobin, impaired mitochondrial respiration, cardiotoxic reactions and tachyarrhythmias associated with the increased sympathetic tone are factors possibly intensifying myocardial infarction. A particularly important factor is that cannabis use is frequently accompanied by tobacco smoking. In conclusion, additional research is warranted to decipher the mechanisms involved, since cannabis use is being legalized increasingly and Δ⁹-tetrahydrocannabinol and its synthetic analogue nabilone are indicated for the treatment of various disease states.

Structure elucidation of the novel synthetic cannabinoid Cumyl-tosyl-indazole-3-carboxamide (Cumyl-TsINACA) found in illicit products in Germany

New chemical moieties continue to appear in synthetic cannabimimetics (SC), the largest group of new psychoactive substances in the EU. We describe the first comprehensive characterisation of the novel SC Cumyl-TsINACA (N-(2-phenylpropan-2-yl)-1-tosyl-1H-indazole-3-carboxamide) from seized case samples. Structure elucidation was performed within the EU-project ADEBAR plus to facilitate confident identification by other researchers and practitioners worldwide. Characteristic MS fragmentations include the cleavage of the sulfonamide bond (S-N), the aryl sulfone bond (C-S) and the elimination rearrangement of SO₂ in the side chain. Cumyl-TsINACA is a full receptor agonist at hCB₁ (E_max = 228%) with very weak binding affinity (K_i = 292 nm) and low functional activity (EC₅₀ = 31 μm). Thermal degradation of Cumyl-TsINACA was observed under GC conditions. The degree to which the tosyl side chain is cleaved due to pyrolysis primarily depends on solvent, the use of glass wool in the liner, and injector temperature. The determination of the constitution by NMR spectroscopy was ambiguous due to the high number of neighbouring, non-proton-bearing atoms. Therefore, other possible structures compatible with the NMR correlations were generated using the WebCocon software. The unambiguous structural evidence was finally obtained by spectra comparison after the synthesis of Cumyl-TsINACA. The low thermal stability, as well as the low affinity and potency, render this compound unfavourable for the use as a psychoactive substance. Thus, we do not expect widespread adoption of this SC.

Synthesis, Molecular Pharmacology, and Structure-Activity Relationships of 3-(Indanoyl)indoles as Selective Cannabinoid Type 2 Receptor Antagonists

Synthetic indole cannabinoids characterized by a 2',2'-dimethylindan-5'-oyl group at the indole C3 position constitute a new class of ligands possessing high affinity for human CB2 receptors at a nanomolar concentration and a good selectivity index. Starting from the neutral antagonist 4, the effects of indole core modification on the pharmacodynamic profile of the ligands were investigated. Several N1 side chains afforded potent and CB2-selective neutral antagonists, notably derivatives 26 (R1 = n-propyl, R2 = H) and 35 (R1 = 4-pentynyl, R2 = H). Addition of a methyl group at C2 improved the selectivity for the CB2 receptor. Moreover, C2 indole substitution may control the CB2 activity as shown by the functionality switch in 35 (antagonist) and 49 (R1 = 4-pentynyl, R2 = CH3, partial agonist).

Cannabinoid receptor type 2 ligands: an analysis of granted patents since 2010

The G-protein-coupled cannabinoid receptor type 2 (CB2R) is a key element of the endocannabinoid (EC) system. EC/CB2R signaling has significant therapeutic potential in major pathologies affecting humans such as allergies, neurodegenerative disorders, inflammation or ocular diseases. CB2R agonism exerts anti-inflammatory and tissue protective effects in preclinical animal models of cardiovascular, gastrointestinal, liver, kidney, lung and neurodegenerative disorders. Existing ligands can be subdivided into endocannabinoids, cannabinoid-like and synthetic CB2R ligands that possess various degrees of potency on and selectivity against the cannabinoid receptor type 1. This review is an account of granted CB2R ligand patents from 2010 up to the present, which were surveyed using Derwent Innovation®.

gem-Difluorination of Methylenecyclopropanes (MCPs) Featuring a Wagner-Meerwein Rearrangement: Synthesis of 2-Arylsubstituted gem-Difluorocyclobutanes

The geminal difluorocyclobutane core is a valuable structural element in medicinal chemistry. Strategies for gem-difluorocyclobutanes, especially the 2-substituted cases, are limiting and often suffer from harsh reaction conditions. Reported herein is a migratory gem-difluorination of aryl-substituted methylenecycloproanes (MCPs) for the synthesis of 2-arylsubstituted gem-difluorocyclobutanes. Commercially available Selectfluor (F-TEDA-BF₄) and Py·HF were used as the fluorine sources. The protocol proceeds via a Wagner-Meerwein rearrangement with mild reaction conditions, good functional group tolerance, and moderate to good yields. The product could be readily transformed to gem-difluorocyclobutane-containing carboxylic acid, amine, and alcohol, all of which are useful building blocks for biologically active molecule synthesis.

Design, Synthesis, and Antimicrobial Activity of Certain New Indole-1,2,4 Triazole Conjugates

The increasing prevalence of microbial infections and the emergence of resistance to the currently available antimicrobial drugs urged the development of potent new chemical entities with eminent pharmacokinetic and/or pharmacodynamic profiles. Thus, a series of new indole-triazole conjugates 6a-u was designed and synthesized to be assessed as new antimicrobial candidates using the diameter of the inhibition zone and minimum inhibitory concentration assays against certain microbial strains. Their in vitro antibacterial evaluation revealed good to moderate activity against most of the tested Gram-negative strains with diameter of the inhibition zone (DIZ) values in the range of 11-15 mm and minimum inhibition concentration (MIC) values around 250 µg/mL. Meanwhile, their in vitro antifungal evaluation demonstrated a potent activity against Candida tropicalis with MIC value as low as 2 µg/mL for most of the tested compounds. Moreover, compound 6f is the most potent congener with an MIC value of 2 µg/mL against Candida albicans.

Isolation of Natural DNA Aptamers for Challenging Small-Molecule Targets, Cannabinoids

Aptamers are nucleic acid-based affinity reagents that are isolated via an in vitro process known as systematic evolution of ligands by exponential enrichment (SELEX). Despite their great potential for a wide range of analytical applications, there are relatively few high-quality small-molecule binding aptamers, especially for "challenging" targets that have low water solubility and/or limited moieties for aptamer recognition. The use of libraries containing chemically modified bases may improve the outcome of some SELEX experiments, but this approach is costly and yields inconsistent results. Here, we demonstrate that a thoughtfully designed SELEX procedure with natural DNA libraries can isolate aptamers with high affinity and specificity for challenging small molecules, including targets for which such selections have previously failed. We first isolate a DNA aptamer with nanomolar affinity and high specificity for (-)-trans-Δ⁹-tetrahydrocannabinol (THC), a target previously thought to be unsuitable for SELEX with natural DNA libraries. We subsequently isolate aptamers that exhibit high affinity and cross-reactivity to two other challenging targets, synthetic cannabinoids UR-144 and XLR-11, while maintaining excellent specificity against a wide range of non-target interferents. Our findings demonstrate that natural nucleic acid libraries can yield high-quality aptamers for small-molecule targets, and we outline a robust workflow for isolating other such aptamers in future selection efforts.

Recent advances in Rh(iii)/Ir(iii)-catalyzed C–H functionalization/annulation via carbene migratory insertion

The review highlighted diverse annulations, including nitrogen, oxygen, sulfur heterocycles and carbocylizations via Rh(iii)/Ir(iii)-catalyzed C–H functionalization/annulation with various arene and carbene precursors.

Cannabinoid Receptor Subtype 2 (CB2R) in a Multitarget Approach: Perspective of an Innovative Strategy in Cancer and Neurodegeneration

The cannabinoid receptor subtype 2 (CB2R) represents an interesting and new therapeutic target for its involvement in the first steps of neurodegeneration as well as in cancer onset and progression. Several studies, focused on different types of tumors, report a promising anticancer activity induced by CB2R agonists due to their ability to reduce inflammation and cell proliferation. Moreover, in neuroinflammation, the stimulation of CB2R, overexpressed in microglial cells, exerts beneficial effects in neurodegenerative disorders. With the aim to overcome current treatment limitations, new drugs can be developed by specifically modulating, together with CB2R, other targets involved in such multifactorial disorders. Building on successful case studies of already developed multitarget strategies involving CB2R, in this Perspective we aim at prompting the scientific community to consider new promising target associations involving HDACs (histone deacetylases) and σ receptors by employing modern approaches based on molecular hybridization, computational polypharmacology, and machine learning algorithms.

Prediction of the Binding Affinities and Selectivity for CB1 and CB2 Ligands Using Homology Modeling, Molecular Docking, Molecular Dynamics Simulations, and MM-PBSA Binding Free Energy Calculations

Cannabinoids are a group of chemical compounds that have been used for thousands of years due to their psychoactive function and systemic physiological effects. There are at least two types of cannabinoid receptors, CB1 and CB2, which belong to the G protein-coupled receptor superfamily and can trigger different signaling pathways to exert their physiological functions. In this study, several representative agonists and antagonists of both CB1 and CB2 were systematically studied to predict their binding affinities and selectivity against both cannabinoid receptors using a set of hierarchical molecular modeling and simulation techniques, including homology modeling, molecular docking, molecular dynamics (MD) simulations and end point binding free energy calculations using the molecular mechanics/Poisson-Boltzmann surface area-WSAS (MM-PBSA-WSAS) method, and molecular mechanics/generalized Born surface area (MM-GBSA) free energy decomposition. Encouragingly, the calculated binding free energies correlated very well with the experimental values and the correlation coefficient square (R²), 0.60, was much higher than that of an efficient but less accurate docking scoring function (R² = 0.37). The hotspot residues for CB1 and CB2 in both active and inactive conformations were identified via MM-GBSA free energy decomposition analysis. The comparisons of binding free energies, ligand-receptor interaction patterns, and hotspot residues among the four systems, namely, agonist-bound CB1, agonist-bound CB2, antagonist-bound CB1, and antagonist-bound CB2, enabled us to investigate and identify distinct binding features of these four systems, with which one can rationally design potent, selective, and function-specific modulators for the cannabinoid receptors.

Synthesis of 2-aryl-benzothiazoles via Ni-catalyzed coupling of benzothiazoles and aryl sulfamates

2-Aryl-benzothiazoles have been successfully synthesized via a simple coupling reaction between benzothiazoles and aryl sulfamates using a nickel catalyst. The nickel catalyst is inexpensive, reusable and commercially available. In addition, the use of highly expensive palladium catalysts and unstable raw materials has been avoided. 2-Aryl-benzothiazoles bearing various substituents on the aryl groups were obtained in good yield.

A Case of Status Epilepticus and Transient Stress Cardiomyopathy Associated with Smoking the Synthetic Psychoactive Cannabinoid, UR-144

Patient: Female, 19-year-old

Final Diagnosis: Status epilepticus and stress induced cardiomyopathy

Symptoms: Seizure

Medication: —

Clinical Procedure: —

Specialty: Toxicology

Synthetic cannabinoids JWH-018, JWH-122, UR-144 and the phytocannabinoid THC activate apoptosis in placental cells

The increasing use of synthetic cannabinoids (SCBs) in recreational settings is becoming a new paradigm of drug abuse. Although SCBs effects mimic those of the Cannabis sativa plant, these drugs are frequently more potent and hazardous. It is known that endocannabinoid signalling plays a crucial role in diverse reproductive events such as placental development. Moreover, the negative impact of the phytocannabinoid Δ⁹-tetrahydrocannabinol (THC) in pregnancy outcome, leading to prematurity, intrauterine growth restriction and low birth weight is well recognized, which makes women of childbearing age a sensitive group to developmental adverse effects of cannabinoids. Placental trophoblast turnover relies on regulated processes of proliferation and apoptosis for normal placental development. Here, we explored the impact of the SCBs JWH-018, JWH-122 and UR-144 and of the phytocannabinoid THC in BeWo cell line, a human placental cytotrophoblast cell model. All the cannabinoids caused a significant decrease in cell viability without LDH release, though this effect was only detected for the highest concentrations of THC. Moreover, a cell cycle arrest at the G₂/M phase was also observed. JWH-018 and JWH-122 increased reactive oxygen species (ROS) production and THC, UR-144 and JWH-122 caused loss of mitochondrial membrane potential. All the compounds were able to induce caspase-9 activation. The involvement of apoptotic pathways was further confirmed through the significant increase in caspase -3/-7 activities. For UR-144, this effect was reversed by the CB1 antagonist AM281, for JWH-018 and THC this effect was mediated by both cannabinoid receptors CB1 and CB2 while for JWH-122 it was cannabinoid receptor-independent. This work demonstrates that THC and SCBs are able to induce apoptotic cell death. Although they may act through different mechanisms and potencies, the studied cannabinoids have the potential to disrupt gestational fundamental events.

Tentative identification of the metabolites of (1-(cyclohexylmethyl)-1H-indol-3-yl)-(2,2,3,3-tetramethylcyclopropyl)methanone, and the product of its thermal degradation, by in vitro and in vivo methods

Synthetic cannabinoids (SCs), mimicking the psychoactive effects of cannabis, consist of a vast array of structurally diverse compounds. A novel compound belonging to the SC family, (1-(cyclohexylmethyl)-1H-indol-3-yl)-(2,2,3,3-tetramethylcyclopropyl)methanone (named TMCP-CHM in this article) contains a cyclopropane ring that isomerizes during the smoking process, resulting in a ring-opened thermal degradant with a terminal double bond in its structure. Metabolites of TMCP-CHM were tentatively identified in vitro (after incubation of the parent substance with S9 pooled human liver fraction) and in vivo (rat experimental model) studies by accurate-mass liquid chromatography-tandem mass spectrometry (LC-MS/MS). For the identification of the degradant metabolites, and to study biotransformation of parent substance in the human, urine and hair samples from patients, who had ingested the compound and were subsequently admitted to hospital with drug intoxications, were analyzed. Products of mono-, di-, trihydroxylation, carboxylation, and carboxylation combined with hydroxylation of TMCP-CHM and its degradant were detected in human urine. Metabolism of the degradant included addition of water to the terminal double bond followed by dehydration and formation of a cyclic metabolite. Degradant metabolites prevailed in comparison with metabolites of the parent substance in each metabolite group examined, except carboxylation. N-Dealkylated metabolites found in human urine originated only from the degradant. Most of the hydroxy metabolites were detected in human urine in both the free form and as glucuronides. The detection of monohydroxylated (M1.1-M1.3, M/A1.10) and carboxylated/hydroxylated (M4.2, M/A4.3) metabolites of TMCP-CHM and the hydrated form of the monohydroxylated metabolite of the degradant was found to be convenient for routine analysis.

Protein-ligand interaction-guided discovery of novel VEGFR-2 inhibitors

As an effective target in abnormal angiogenesis-related tumor treatment, VEGFR-2 has small-molecule inhibitors of various scaffolds being approved for treating diseases such as renal carcinoma, non-small cell lung cancer, etc. However, endogenous and acquired drug resistance are still considered to be the main contributors for the failure of VEGFR-2 clinical candidates. Therefore, development of novel VEGFR-2 inhibitors is still urgently needed in the market but also challenging. In this work, residues including Asp1046, Ile1025, HIS1026, Cys919 and Lys868 were identified as the most important residues for Hbonded interaction, while His1026, Asp1046, Glu885, Ile1025 and Leu840 exhibited critical role for the nonbonded interactions through a comprehensive analysis of protein-ligand interactions, which plays critical roles in the binding of compounds and targets. Guided by the analysis of binding interactions, a total of 10 novel VEGFR-2 inhibitors based on N-methyl-4-oxo-N-propyl-1,4-dihydroquinoline-2-carboxamide scaffold were discovered through fragment-based drug design and structure-based virtual screening, which expands the chemical space of current VEGFR-2 inhibitors. Biological activity evaluation showed that even though the enzymatic activity of these compounds against VEGFR-2 were inferior to that of the positive controls sorafenib and motesanib, compound I-10 showed moderate HepG2 cell inhibitory activity with an IC₅₀ value of 33.65 μM and eight compounds exhibited moderate or higher HUVEC inhibitory activity in the range of 19.54-57.98 μM compared to the controls. Particularly, the HUVEC inhibitory activity of compound I-6 (IC₅₀ = 19.54 μM) outperformed motesanib and can be used as starting points for further optimization and development for cancer treatment.Communicated by Ramaswamy H. Sarma.

Synthesis and in vitro evaluation of fluorine-18 benzimidazole sulfones as CB2 PET-radioligands

Cannabinoid type 2 receptor (CB2) is up-regulated on activated microglial cells and can potentially be used as a biomarker for PET-imaging of neuroinflammation. In this study the synthesis and pharmacological evaluation of novel fluorinated pyridyl and ethyl sulfone analogues of 2-(tert-butyl)-5-((2-fluoropyridin-4-yl)sulfonyl)-1-(2-methylpentyl)-1H-benzo[d]imidazole (rac-1a) are described. In general, the ligands showed low nanomolar potency (CB2 EC₅₀ < 10 nM) and excellent selectivity over the CB1 subtype (>10 000×). Selected ligands 1d, 1e, 1g and 3l showing high CB2 binding affinity (K_i < 10 nM) were radiolabelled with fluorine-18 from chloropyridyl and alkyl tosylate precursors with good to high isolated radioactive yields (25-44%, non-decay corrected, at the end of synthesis). CB2-specific binding of the radioligand candidates [¹⁸F]-1d and [¹⁸F]-3l was assessed on rat spleen cryosections using in vitro autoradiography. The results warrant further in vivo evaluation of the tracer candidates as prospective CB2 PET-imaging agents.

Synthesis of indoles and quinazolines via additive-controlled selective C–H activation/annulation of N-arylamidines and sulfoxonium ylides

Selective synthesis of indoles and quinazolines was achieved through a precise control of C–H activation/annulation by changing additives.

Exploring the effectiveness of novel benzimidazoles as CB2 ligands: synthesis, biological evaluation, molecular docking studies and ADMET prediction

Herein we continued our previous work on the development of CB2 ligands, reporting the design and synthesis of a series of benzimidazole-containing derivatives that were explored as selective CB2 ligands with binding affinity towards both CB1 and CB2 receptors. Seven out of eighteen compounds exhibited preferential binding ability to CB2 over CB1 receptors with potencies in the sub-micromolar or low micromolar range. In particular, we identified two promising hit compounds, the agonist 1-[2-(N,N-diethylamino)ethyl]-2-(4-ethoxybenzyl)-5-trifluoromethylbenzimidazole (3) (CB2: K _i = 0.42 μM) and the inverse agonist/antagonist 1-butyl-2-(3,4-dichlorobenzyl)-5-trifluoromethylbenzimidazole (11) (CB2: K _i = 0.37 μM). Docking studies also performed on other benzimidazoles reported in the literature supported the structure-activity relationship observed in this series of compounds and allowed the key contacts involved in the agonist and/or inverse agonist behaviour displayed by these derivatives to be determined. The in silico evaluation of ADMET properties suggested a favorable pharmacokinetic and safety profile, promoting the drug-likeness of these compounds towards a further optimization process.

Synthetic cannabinoids are substrates and inhibitors of multiple drug-metabolizing enzymes

Synthetic cannabinoids, a new class of psychoactive substances, are potent agonists of cannabinoid receptors, which mimic the psychoactive effects of the principal psychoactive component of cannabis, ∆9-tetrahydrocannabinol. Despite governmental scheduling as illicit drugs, new synthetic cannabinoids are being produced. The abuse of synthetic cannabinoids with several drugs containing different chemical groups has resulted in large numbers of poisonings. This has increased the urgency for forensic and public health laboratories to identify the metabolites of synthetic cannabinoids and apply this knowledge to the development of analytical methods and for toxicity prediction. It is necessary to determine whether synthetic cannabinoids are involved in drug-metabolizing enzyme-mediated drug-drug interactions. This review describes the metabolic pathways of 13 prevalent synthetic cannabinoids and various drug-metabolizing enzymes responsible for their metabolism, including cytochrome P450 (CYP), UDP-glucuronosyltransferases (UGTs), and carboxylesterases. The inhibitory effects of synthetic cannabinoids on CYP and UGT activities are also reviewed to predict the potential of synthetic cannabinoids for drug-drug interactions. The drug-metabolizing enzymes responsible for metabolism of synthetic cannabinoids should be characterized and the effects of synthetic cannabinoids on CYP and UGT activities should be determined to predict the pharmacokinetics of synthetic cannabinoids and synthetic cannabinoid-induced drug-drug interactions in the clinic.

The synthetic cannabinoid XLR-11 induces in vitro nephrotoxicity by impairment of endocannabinoid-mediated regulation of mitochondrial function homeostasis and triggering of apoptosis

Synthetic cannabinoids (SCBs)-related intoxications and deaths have been increasingly reported, turning its widespread recreational use into a major public health concern. Specifically, a direct link between SCBs and acute kidney injury (AKI) has been established. XLR-11 is an SCB commonly found in the toxicological analysis of patients with SCB-associated AKI. However, the pathophysiology of AKI among SCB consumers remains unknown. This work thus represents the first in vitro assessment of SCB nephrotoxicity, as a first approach to identify its cellular targets. We demonstrate that XLR-11, at biologically relevant concentrations (in the nanomolar range), primarily targets mitochondrial function in human proximal tubule (HK-2) cells, inducing a transient hyperpolarization of the mitochondrial membrane and increasing ATP production, accompanied by Bax translocation from cytosol into mitochondria. These phenomena further triggered energy-dependent apoptotic cell death pathways, indicated by increased caspase-3 activity and chromatin condensation. Experiments using SR141716A and SR144258, specific antagonists for CB1 and CB2 receptors, respectively, as well as HEK293T cells (which do not express CBRs) highlighted these processes' dependence on CBR activation. Nevertheless, ATP formation seemed to follow a CBR-independent pathway. Our findings using specific inhibitors of endogenous cannabinoids biosynthesis (i.e. MAFP and THL) further evidenced the involvement of the endocannabinoid system in the regulation of these processes, as XLR-11 binding to CBRs seemed to compromise endocannabinoid-mediated preservation of mitochondrial function. Nevertheless, the exact mechanisms involved require further clarification.

Discriminative Stimulus Properties of Phytocannabinoids, Endocannabinoids, and Synthetic Cannabinoids

Psychoactive cannabinoids from the marijuana plant (phytocannabinoids), from the body (endocannabinoids), and from the research lab (synthetic cannabinoids) produce their discriminative stimulus effects by stimulation of CB1 receptors in the brain. Early discrimination work with phytocannabinoids confirmed that Δ9-tetrahydrocannabinol (Δ9-THC) is the primary psychoactive constituent of the marijuana plant, with more recent work focusing on characterization of the contribution of the major endocannabinoids, anandamide and 2-arachidonoylglycerol (2-AG), to Δ9-THC-like internal states. Collectively, these latter studies suggest that endogenous increases in both anandamide and 2-AG seem to be optimal for mimicking Δ9-THC's discriminative stimulus effects, although suprathreshold concentrations of anandamide also appear to be Δ9-THC-like in discrimination assays. Recently, increased abuse of synthetic cannabinoids (e.g., "fake marijuana") has spurred discrimination studies to inform regulatory authorities by predicting which of the many synthetic compounds on the illicit market are most likely to share Δ9-THC's abuse liability. In the absence of a reliable model of cannabinoid self-administration (specifically, Δ9-THC self-administration), cannabinoid discrimination represents the most validated and pharmacologically selective animal model of an abuse-related property of cannabinoids - i.e., marijuana's subjective effects. The influx of recent papers in which cannabinoid discrimination is highlighted attests to its continued relevance as a valuable method for scientific study of cannabinoid use and abuse.

The Chemistry and Pharmacology of Synthetic Cannabinoid Receptor Agonist New Psychoactive Substances: Evolution

Synthetic cannabinoid receptor agonists (SCRAs) are the largest and most structurally diverse class of new psychoactive substances (NPS). Although the earliest SCRA NPS were simply repurposed from historical academic manuscripts or pharmaceutical patents describing cannabinoid ligands, recent examples bear hallmarks of rational design. SCRA NPS manufacturers have applied traditional medicinal chemistry strategies (such as molecular hybridization, bioisosteric replacement, and scaffold hopping) to existing cannabinoid templates in order to generate new molecules that circumvent structure-based legislation. Most SCRAs potently activate cannabinoid type 1 and type 2 receptors (CB₁ and CB₂, respectively), with the former contributing to the psychoactivity of these substances. SCRAs are generally more toxic than the Δ⁹-tetrahydrocannabinol (Δ⁹-THC) found in cannabis, and this may be due to ligand bias, metabolism, or off-target activity. This chapter will chart the evolution of recently identified SCRA NPS chemotypes, as well as their putative manufacturing by-products and thermolytic degradants, and describe structure-activity relationships within each class.

The Chemistry and Pharmacology of Synthetic Cannabinoid Receptor Agonists as New Psychoactive Substances: Origins

Synthetic cannabinoid receptor agonists (SCRAs) have proliferated as new psychoactive substances (NPS) over the past decade. Relative to other classes of NPS, SCRAs are structurally heterogeneous; however, most SCRAs act as potent, high-efficacy agonists of cannabinoid type 1 and type 2 receptors (CB₁ and CB₂, respectively). Characterization of the pharmacology and toxicology of these substances is hindered by the dynamic nature of the SCRA marketplace. Beyond basic pharmacological profiling at CB₁ and CB₂ receptors, very little is known about the acute or chronic effects of SCRAs. Many of the effects of SCRAs are qualitatively similar to those of the Δ⁹-tetrahydrocannabinol (Δ⁹-THC) found in cannabis. However, unlike Δ⁹-THC, SCRAs are frequently associated with serious adverse effects, including cardiotoxicity, nephrotoxicity, and death. This chapter will provide an overview of the structure and function of the primary target for SCRAs, the CB₁ receptor, and survey the structure-activity relationships of the historical SCRAs that served as templates for the earliest generations of NPS.

Lateral flow immunoassay and enzyme linked immunosorbent assay as effective immunomethods for the detection of synthetic cannabinoid JWH-200 based on the newly synthesized hapten

In recent years, the use of synthetic cannabinoids (SCs) as drugs of abuse has greatly increased. SCs are associated with a risk of severe poisoning or even death. Therefore, more rapid, cost effective and reliable methods are needed, especially for the screening of drivers after traffic accidents and for detailed toxicological analysis in forensic laboratories. In this study, we developed a lateral flow immunoassay (LFIA) and an enzyme linked immunosorbent assay (ELISA) for the detection of JWH-200 in oral fluids. For this purpose a new hapten was prepared using a ten-step synthetic route. The developed immuno methods are based on antibodies obtained from rabbit immunized with synthesized hapten conjugated to carrier protein. The proposed methods are highly sensitive (LOD_LFIA = 0.08 ± 0.04 ng mL^-1; LOD_ELISA = 0.04 ± 0.02 ng mL^-1). They were applied to the quantification of JHW-200 in spiked oral fluids. The recoveries ranged from 82 to 134% for both methods. The results correlated excellently with results obtained using UHPLC-MS/MS (R²_LFIA = 0.99; R²_ELISA = 0.99). Our developed methods could be an important tool for analyses of JWH-200 in human oral fluids. The one-step LFIA is particularly suitable for roadside and on-site monitoring due to the rapid qualitative results it delivers, while the ELISA is especially useful for laboratory quantitative analyses of positive samples captured by LFIA.

Amidoalkylindoles as Potent and Selective Cannabinoid Type 2 Receptor Agonists with in Vivo Efficacy in a Mouse Model of Multiple Sclerosis

Selective CB₂ agonists represent an attractive therapeutic strategy for the treatment of a variety of diseases without psychiatric side effects mediated by the CB₁ receptor. We carried out a rational optimization of a black market designer drug SDB-001 that led to the identification of potent and selective CB₂ agonists. A 7-methoxy or 7-methylthio substitution at the 3-amidoalkylindoles resulted in potent CB₂ antagonists (27 or 28, IC₅₀ = 16-28 nM). Replacement of the amidoalkyls from 3-position to the 2-position of the indole ring dramatically increased the agonist selectivity on the CB₂ over CB₁ receptor. Particularly, compound 57 displayed a potent agonist activity on the CB₂ receptor (EC₅₀ = 114-142 nM) without observable agonist or antagonist activity on the CB₁ receptor. Furthermore, 57 significantly alleviated the clinical symptoms and protected the murine central nervous system from immune damage in an experimental autoimmune encephalomyelitis (EAE) mouse model of multiple sclerosis.

Perspectives of Cannabinoid Type 2 Receptor (CB2R) Ligands in Neurodegenerative Disorders: Structure-Affinity Relationship (SAfiR) and Structure-Activity Relationship (SAR) Studies

Up-regulation of CB2R on activated microglial cells, the first step in neurodegeneration, has been widely demonstrated, and this finding makes the receptor a promising target in the early diagnosis and treatment of several neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and multiple sclerosis (MS). The development of CB2R PET ligands could help demonstrate the neurodegenerative pathogenesis, thus providing useful tools for characterizing the role of neuroinflammation in the progression of these disorders. CB2R agonists and inverse agonists have emerged as neuroprotective agents, and CB2R agonists have entered several clinical trials. CB2R ligands have therefore received great attention, and different molecular scaffolds have been selected to target CB2R subtypes. This review is focused on structure-activity relationship (SAR) and structure-affinity relationship (SAfiR) studies performed on different scaffolds with the aim to identify the molecular features useful for the design of both therapeutic and diagnostic agents.

Disruption of hippocampal synaptic transmission and long-term potentiation by psychoactive synthetic cannabinoid 'Spice' compounds: comparison with Δ9 -tetrahydrocannabinol

There has been a marked increase in the availability of synthetic drugs designed to mimic the effects of marijuana. These cannabimimetic drugs, sold illicitly as 'Spice' and related products, are associated with serious medical complications in some users. In vitro studies suggest that synthetic cannabinoids in these preparations are potent agonists at central cannabinoid CB1 receptors (CB1Rs), but few investigations have delineated their cellular effects, particularly in comparison with the psychoactive component of marijuana, Δ9 -tetrahydrocannabinol (Δ9 -THC). We compared the ability of three widely abused synthetic cannabinoids and Δ9 -THC to alter glutamate release and long-term potentiation in the mouse hippocampus. JWH-018 was the most potent inhibitor of hippocampal synaptic transmission (EC50 ~15 nM), whereas its fluoropentyl derivative, AM2201, inhibited synaptic transmission with slightly lower potency (EC50 ~60 nM). The newer synthetic cannabinoid, XLR-11, displayed much lower potency (EC50 ~900 nM) that was similar to Δ9 -THC (EC50 ~700 nM). The effects of all compounds occurred via activation of CB1Rs, as demonstrated by reversal with the selective antagonist/inverse agonist AM251 or the neutral CB1R antagonist PIMSR1. Moreover, AM2201 was without effect in the hippocampus of transgenic mice lacking the CB1R. Hippocampal slices exposed to either synthetic cannabinoids or Δ9 -THC exhibited significantly impaired long-term potentiation (LTP). We find that, compared with Δ9 -THC, the first-generation cannabinoids found in Spice preparations display higher potency, whereas a recent synthetic cannabinoid is roughly equipotent with Δ9 -THC. The disruption of synaptic function by these synthetic cannabinoids is likely to lead to profound impairments in cognitive and behavioral function.

Combination Chemistry: Structure-Activity Relationships of Novel Psychoactive Cannabinoids

Originally developed as research tools for use in structure-activity relationship studies, synthetic cannabinoids contributed to significant scientific advances in the cannabinoid field. Unfortunately, a subset of these compounds was diverted for recreational use beginning in the early 2000s. As these compounds were banned, they were replaced with additional synthetic cannabinoids with increasingly diverse chemical structures. This chapter focuses on integration of recent results with those covered in previous reviews. Whereas most of the early compounds were derived from the prototypic naphthoylindole JWH-018, currently popular synthetic cannabinoids include tetramethylcyclopropyl ketones and indazole-derived cannabinoids (e.g., AB-PINACA, AB-CHMINACA). Despite their structural differences, psychoactive synthetic cannabinoids bind with high affinity to CB1 receptors in the brain and, when tested, have been shown to activate these receptors and to produce a characteristic profile of effects, including suppression of locomotor activity, antinociception, hypothermia, and catalepsy, as well as Δ9-tetrahydrocannabinol (THC)-like discriminative stimulus effects in mice. When they have been tested, synthetic cannabinoids are often found to be more efficacious at activation of the CB1 receptor and more potent in vivo. Further, their chemical alteration by thermolysis during use and their uncertain stability and purity may result in exposure to degradants that differ from the parent compound contained in the original product. Consequently, while their intoxicant effects may be similar to those of THC, use of synthetic cannabinoids may be accompanied by unpredicted, and sometimes harmful, effects.

Pharmacological and Toxicological Effects of Synthetic Cannabinoids and Their Metabolites

Commercial preparations containing synthetic cannabinoids (SCBs) are rapidly emerging as drugs of abuse. Although often assumed to be "safe" and "legal" alternatives to cannabis, reports indicate that SCBs induce toxicity not often associated with the primary psychoactive component of marijuana, Δ9-tetrahydrocannabinol (Δ9-THC). This chapter will summarize the evidence that use of SCBs poses greater health risks relative to marijuana and suggest that distinct pharmacological properties and metabolism of SCBs relative to Δ9-THC may contribute to this increased toxicity. Studies reviewed will indicate that in contrast to partial agonist properties of Δ9-THC typically observed in vitro, SCBs act as full CB1 and CB2 receptor agonists both in cellular assays and animal studies. Furthermore, unlike Δ9-THC metabolism, several SCB metabolites retain high affinity for and exhibit a range of intrinsic activities at CB1 and CB2 receptors. Finally, the potential for SCBs to cause adverse drug-drug interactions with other drugs of abuse, as well as with common therapeutic agents, will be discussed. Collectively, the evidence provided in this chapter indicates that SCBs should not be considered safe and legal alternatives to marijuana. Instead, the enhanced toxicity of SCBs relative to marijuana, perhaps resulting from the combined actions of a complex mixture of different SCBs present and their active metabolites that retain high affinity for CB1 and CB2 receptors, highlights the inherent danger that may accompany use of these substances.

Stratification of Cannabinoid 1 Receptor (CB1R) Agonist Efficacy: Manipulation of CB1R Density through Use of Transgenic Mice Reveals Congruence between In Vivo and In Vitro Assays

Synthetic cannabinoids (SCs) are an emerging class of abused drugs that differ from each other and the phytocannabinoid ∆⁹-tetrahydrocannabinol (THC) in their safety and cannabinoid-1 receptor (CB₁R) pharmacology. As efficacy represents a critical parameter to understanding drug action, the present study investigated this metric by assessing in vivo and in vitro actions of THC, two well-characterized SCs (WIN55,212-2 and CP55,940), and three abused SCs (JWH-073, CP47,497, and A-834,735-D) in CB₁ (+/+), (+/-), and (-/-) mice. All drugs produced maximal cannabimimetic in vivo effects (catalepsy, hypothermia, antinociception) in CB₁ (+/+) mice, but these actions were essentially eliminated in CB₁ (-/-) mice, indicating a CB₁R mechanism of action. CB₁R efficacy was inferred by comparing potencies between CB₁ (+/+) and (+/-) mice [+/+ ED₅₀ /+/- ED₅₀], the latter of which has a 50% reduction of CB₁Rs (i.e., decreased receptor reserve). Notably, CB₁ (+/-) mice displayed profound rightward and downward shifts in the antinociception and hypothermia dose-response curves of low-efficacy compared with high-efficacy cannabinoids. In vitro efficacy, quantified using agonist-stimulated [³⁵S]GTPγS binding in spinal cord tissue, significantly correlated with the relative efficacies of antinociception (r = 0.87) and hypothermia (r = 0.94) in CB₁ (+/-) mice relative to CB₁ (+/+) mice. Conversely, drug potencies for cataleptic effects did not differ between these genotypes and did not correlate with the in vitro efficacy measure. These results suggest that evaluation of antinociception and hypothermia in CB₁ transgenic mice offers a useful in vivo approach to determine CB₁R selectivity and efficacy of emerging SCs, which shows strong congruence with in vitro efficacy.