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

Pharmacological evaluation of synthetic cannabinoids identified as constituents of spice

In recent years, many synthetic cannabinoid (CB) receptor agonists have appeared on the market as constituents of herbal incense mixtures known as "spice". Contrary to the declared use, they are perorally consumed as a replacement for marijuana to get "high". In many cases, detailed information on the physicochemical and pharmacological properties of the synthetic compounds found in spice preparations is lacking. We have now evaluated a large series of heterocyclic compounds, 1,3-disubstituted indole and 2-azaindole derivatives known or assumed to be CB₁ receptor agonists, many of which have previously been identified in forensic samples. The mainly observed structural variations to circumvent restriction by law were bioisosteric exchanges of functional groups in known CB₁ agonists. We analyzed the structure-activity relationships of compounds at human CB₁ and CB₂ receptors based on affinities obtained in radioligand binding studies, and determined their efficacy in cAMP accumulation assays. Moreover, we investigated the activities of the compounds at the orphan G protein-coupled receptors GPR18 and GPR55 both of which are known to interact with cannabinoids. Most of the investigated compounds behaved as potent full agonists of CB₁ and CB₂ receptors with affinities in the low nanomolar to subnanomolar concentration range. Some compounds were moderately potent GPR55 antagonists, while none interacted with GPR18. Most derivatives were predicted to cross the blood-brain barrier as determined by bioinformatics tools. These data are useful for assessing synthetic cannabinoids and will be helpful for predicting pharmacological properties of novel compounds that appear on the illicit drug market.

Δ9-Tetrahydrocannabinol-like effects of novel synthetic cannabinoids found on the gray market

When synthetic cannabinoid compounds became controlled by state and federal governments, different, noncontrolled compounds began to appear as marijuana substitutes. Unlike the scheduled cannabinoids, the newer compounds have not been characterized for potency and efficacy in preclinical studies. The purpose of these experiments was to determine whether some of the more recent synthetic compounds sold as marijuana substitutes have behavioral effects similar to those of Δ-tetrahydrocannabinol (Δ-THC), the pharmacologically active compound in marijuana. The compounds UR-144, XLR-11, AKB-48 (APINACA), PB-22 (QUPIC), 5F-PB-22, and AB-FUBINACA were tested for locomotor depressant effects in male Swiss-Webster mice and subsequently for their ability to substitute for Δ-THC (3 mg/kg, intraperitoneally) in drug discrimination experiments with male Sprague-Dawley rats. UR-144, XLR-11, AKB-48, and AB-FUBINACA each decreased locomotor activity for up to 90 min, whereas PB-22 and 5F-PB-22 produced depressant effects lasting 120-150 min. Each of the compounds fully substituted for the discriminative stimulus effects of Δ-THC. These findings confirm the suggestion that these compounds have marijuana-like psychoactive effects and abuse liability.

Analysis of Parent Synthetic Cannabinoids in Blood and Urinary Metabolites by Liquid Chromatography Tandem Mass Spectrometry

Synthetic cannabinoids emerged on the designer drug market in recent years due to their ability to produce cannabis-like effects without the risk of detection by traditional drug testing techniques such as immunoassay and gas chromatography-mass spectrometry. As government agencies work to schedule existing synthetic cannabinoids, new, unregulated and structurally diverse compounds continue to be developed and sold. Synthetic cannabinoids undergo extensive metabolic conversion. Consequently, both blood and urine specimens may play an important role in the forensic analysis of synthetic cannabinoids. It has been observed that structurally similar synthetic cannabinoids follow common metabolic pathways, which often produce metabolites with similar metabolic transformations. Presented are two validated quantitative methods for extracting and identifying 15 parent synthetic cannabinoids in blood, 17 synthetic cannabinoid metabolites in urine and the qualitative identification of 2 additional parent compounds. The linear range for most synthetic cannabinoid compounds monitored was 0.1-10 ng/mL with the limit of detection between 0.01 and 0.5 ng/mL. Selectivity, specificity, accuracy, precision, recovery and matrix effect were also examined and determined to be acceptable for each compound. The validated methods were used to analyze a compilation of synthetic cannabinoid investigative cases where both blood and urine specimens were submitted. The study suggests a strong correlation between the metabolites detected in urine and the parent compounds found in blood.

Next generation of novel psychoactive substances on the horizon - A complex problem to face

BACKGROUND

The last decade has seen a rapid and continuous growth in the availability and use of novel psychoactive substances (NPS) across the world. Although various products are labeled with warnings "not for human consumption", they are intended to mimic psychoactive effects of illicit drugs of abuse. Once some compounds become regulated, new analogues appear in order to satisfy consumers' demands and at the same time to avoid criminalization. This review presents updated information on the second generation of NPS, introduced as replacements of the already banned substances from this class, focusing on their pharmacological properties and metabolism, routes of administration, and effects in humans.

METHODS

Literature search, covering years 2013-2015, was performed using the following keywords alone or in combination: "novel psychoactive substances", "cathinones", "synthetic cannabinoids", "benzofurans", "phenethylamines", "2C-drugs", "NBOMe", "methoxetamine", "opioids", "toxicity", and "metabolism".

RESULTS

More than 400 NPS have been reported in Europe, with 255 detected in 2012-2014. The most popular are synthetic cannabimimetics and psychostimulant cathinones; use of psychedelics and opioids is less common. Accumulating experimental and clinical data indicate that potential harms associated with the use of second generation NPS could be even more serious than those described for the already banned drugs.

CONCLUSIONS

NPS are constantly emerging on the illicit drug market and represent an important health problem. A significant amount of research is needed in order to fully quantify both the short and long term effects of the second generation NPS, and their interaction with other drugs of abuse.

Emerging drugs of abuse: current perspectives on synthetic cannabinoids

New psychoactive drugs that have appeared over the last decade are typically dominated by cathinones and synthetic cannabinoids (SCs). SCs have been emerging as recreational drugs because they mimic the euphoria effect of cannabis while still being legal. Sprayed on natural herb mixtures, SCs have been primarily sold as "herbal smoking blends" or "herbal incense" under brand names like "Spice" or "K2". Currently, SCs pure compounds are available from websites for the combination with herbal materials or for the use in e-cigarettes. For the past 5 years, an ever increasing number of compounds, representative of different chemical classes, have been promoted and now represent a large assortment of new popular drugs of abuse, which are difficult to properly identify. Their legal status varies by country with many government institutions currently pushing for their control. The in vitro binding to CB1/CB2 receptors is usually well-known and considerable differences have been found in the CB1 versus CB2 selectivity and potency within the different SCs, with several structure-activity relations being evident. Desired effects by CB1 agonist users are relaxation/recreative, however, cardiovascular, gastrointestinal, or psychiatric/neurological side effects are commonly reported. At present there is no specific antidote existing if an overdose of designer drugs was to occur, and no curative treatment has been approved by health authorities. Management of acute toxic effects is mainly symptomatic and extrapolated from experience with cannabis.

Effects of bioisosteric fluorine in synthetic cannabinoid designer drugs JWH-018, AM-2201, UR-144, XLR-11, PB-22, 5F-PB-22, APICA, and STS-135

Synthetic cannabinoid (SC) designer drugs featuring bioisosteric fluorine substitution are identified by forensic chemists and toxicologists with increasing frequency. Although terminal fluorination of N-pentyl indole SCs is sometimes known to improve cannabinoid type 1 (CB1) receptor binding affinity, little is known of the effects of fluorination on functional activity of SCs. This study explores the in vitro functional activities of SC designer drugs JWH-018, UR-144, PB-22, and APICA, and their respective terminally fluorinated analogues AM-2201, XLR-11, 5F-PB-22, and STS-135 at human CB1 and CB2 receptors using a FLIPR membrane potential assay. All compounds demonstrated agonist activity at CB1 (EC50 = 2.8-1959 nM) and CB2 (EC50 = 6.5-206 nM) receptors, with the fluorinated analogues generally showing increased CB1 receptor potency (∼2-5 times). Additionally, the cannabimimetic activities and relative potencies of JWH-018, AM-2201, UR-144, XLR-11, PB-22, 5F-PB-22, APICA, and STS-135 in vivo were evaluated in rats using biotelemetry. All SCs dose-dependently induced hypothermia and reduced heart rate at doses of 0.3-10 mg/kg. There was no consistent trend for increased potency of fluorinated SCs over the corresponding des-fluoro SCs in vivo. Based on magnitude and duration of hypothermia, the SCs were ranked for potency (PB-22 > 5F-PB-22 = JWH-018 > AM-2201 > APICA = STS-135 = XLR-11 > UR-144).

Case reports of synthetic cannabinoid XLR-11 associated fatalities

Synthetic cannabinoids have been available in herbal incense and potpourri products over the Internet and in smoke shops for the last several years. We report the deaths of two individuals that were associated with XLR-11. Specimens were extracted via a liquid-liquid extraction at basic pH into hexane:ethyl acetate and analyzed by liquid chromatography tandem mass spectrometry. For these two case reports, we describe the instrumental analysis and extraction methods for XLR-11, toxicological results for postmortem blood specimens, relevant case information and autopsy findings. We also briefly review any previously published peer-reviewed reports in which XLR-11 was analytically confirmed and determined to be an intoxicating agent.

The Influence of Synthetic Cannabinoid UR-144 on Human Psychomotor Performance--A Case Report Demonstrating Road Traffic Risks

OBJECTIVE

UR-144 [(1-pentyl-1H-indol-3-yl)(2,2,3,3-tetramethylcyclopropyl)-methanone] is a synthetic cannabinoid, which has been detected in many "legal highs" seized from the global drug market since the beginning of 2012. It gained popularity as a "legal" alternative to classic cannabis in countries where it was not controlled. The popularity of UR-144 means that this substance is also abused by individuals driving motor vehicles. This article describes a case of driving under the influence (DUI) of UR-144. The aim of the undertaken case analysis and presenting description of pharmacological similarity of THC and UR-144 is to answer the question whether UR-144 can produce effects incompatible with safe driving.

METHODS

Blood from the driver was obtained by a physician approximately 2 h after the collision and 4.5 h after self-reported dosing. Police from the crash site provided behavioral observations, and the physician performed medical examination. Blood was analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The developed method was described in detail. The method was linear in the range of 0.5-50 ng/mL; the precision and accuracy values obtained were less than 15%. The symptoms observed by police and physician who collected the blood sample were described.

RESULTS

In the blood sample collected from the driver, UR-144 and its major pyrolysis product [1-(1-pentyl-1H-indol-3-yl)-3-methyl-2-(propan-2-yl)but-3-en-1-one] were detected. Whole-blood concentration of UR-144 was 14.6 ng/mL. The result of blood analysis and observed symptoms clearly indicated that the driver was under the influence of UR-144.

CONCLUSIONS

UR-144 produces effects and impairment similar to or even more dangerous than delta-9-tetrahydrocannabinol (Δ(9)-THC), making it unsafe for driving. Therefore, UR-144 should be treated as a potentially dangerous substance in traffic safety.

Genotoxic properties of representatives of alkylindazoles and aminoalkyl-indoles which are consumed as synthetic cannabinoids

Synthetic cannabinoids (SCs) cause similar effects as cannabis and are sold in herbal mixtures. Recent investigations indicate that some of these drugs possess genotoxic properties. Therefore, we tested representatives of two groups, namely, aminoalkylindoles (AM-2201 and UR-144) and 1-alkylindazoles (5F-AKB-48 and AM-2201-IC) in single cell gel electrophoresis and micronucleus (MN) assays with human lymphocytes and in Salmonella/microsome assays. All drugs except AM-2201 caused DNA-migration, the LOELs were between 50 and 75 µM. Furthermore, all SCs caused inhibition of cell division and significant induction of MN which reflect structural and numerical chromosomal aberrations. The LOEL values were 50 µM for UR-144 and 5-AKB-48 and 75 µM for the other drugs. Also the levels of nucleoplasmatic bridges which are formed from dicentric chromosomes were elevated under identical conditions while the frequencies of nuclear buds were not affected. These findings show that representatives of both groups cause chromosomal damage while the negative results in Salmonella assays (in strains TA98, TA100, TA1535, TA1537 and TA102) in absence and presence of metabolic activation indicate that they do not induce gene mutations. Taken together, these findings indicate that SCs may cause adverse health effects in users as a consequence of damage of the genetic material.

Bioisosteric Fluorine in the Clandestine Design of Synthetic Cannabinoids

Over the past decade, a plethora of indole-based synthetic cannabinoids (SCs) have emerged with their structures clearly inspired by scientific literature. Their structures continually evolve to elude detection by law enforcement and circumvent finite scheduling laws. The latest generation of SCs follow patent literature that encompasses a bioisosteric fluorine-for-hydrogen replacement commonly applied in medicinal chemistry. Unlike traditional pharmaceutical development, where rigorous preclinical evaluation is completed before human administration, these SCs are distributed for intended recreational consumption with little-to-no pharmacological data known. This highlight explores the evolution of SCs to this latest generation of fluorinated SCs where accumulating evidence indicates increased health concerns.

3D-QSAR/CoMFA-based structure-affinity/selectivity relationships of aminoalkylindoles in the cannabinoid CB1 and CB2 receptors

A 3D-QSAR (CoMFA) study was performed in an extensive series of aminoalkylindoles derivatives with affinity for the cannabinoid receptors CB1 and CB2. The aim of the present work was to obtain structure-activity relationships of the aminoalkylindole family in order to explain the affinity and selectivity of the molecules for these receptors. Major differences in both, steric and electrostatic fields were found in the CB1 and CB2 CoMFA models. The steric field accounts for the principal contribution to biological activity. These results provide a foundation for the future development of new heterocyclic compounds with high affinity and selectivity for the cannabinoid receptors with applications in several pathological conditions such as pain treatment, cancer, obesity and immune disorders, among others.

Hypervalent iodine mediated direct one pot transformation of aldehydes to ketones

An environmentally benign, step economical synthesis of ketones directly from aldehydes has been developed using hypervalent iodine as an oxidant.

Optimization of novel indole-2-carboxamide inhibitors of neurotropic alphavirus replication

Neurotropic alphaviruses, which include western equine encephalitis virus (WEEV) and Fort Morgan virus, are mosquito-borne pathogens that infect the central nervous system causing acute and potentially fatal encephalitis. We previously reported a novel series of indole-2-carboxamides as alphavirus replication inhibitors, one of which conferred protection against neuroadapted Sindbis virus infection in mice. We describe here further development of this series, resulting in 10-fold improvement in potency in a WEEV replicon assay and up to 40-fold increases in half-lives in mouse liver microsomes. Using a rhodamine123 uptake assay in MDR1-MDCKII cells, we were able to identify structural modifications that markedly reduce recognition by P-glycoprotein, the key efflux transporter at the blood-brain barrier. In a preliminary mouse PK study, we were able to demonstrate that two new analogues could achieve higher and/or longer plasma drug exposures than our previous lead and that one compound achieved measurable drug levels in the brain.

Analysis of UR-144 and its pyrolysis product in blood and their metabolites in urine

UR-144 [(1-pentyl-1H-indol-3-yl)(2,2,3,3-tetramethylcyclopropyl)methanone] is a synthetic cannabinoid, which has been detected in many herbal blends, resinous samples and powders seized from the Polish drug market since the beginning of 2012. This paper presents the case of intoxication by this substance. A complete picture of the symptoms observed by a witness, paramedics and medical doctors are given. In the analysis of powder residues from the plastic bag seized from the intoxicated person by gas chromatography-mass spectrometry (GC-MS), UR-144 and its major pyrolysis product [1-(1-pentyl-1H-indol-3-yl)-3-methyl-2-(propan-2-yl)but-3-en-1-one] were detected. Both substances were also identified in a blood sample collected on admission of the patient to hospital using liquid chromatography-triple quadrupole tandem mass spectrometry (LC-QqQ-MS). Blood concentration of UR-144 was 6.1 ng/mL. A urine sample collected at the same time was analyzed by liquid chromatography-quadruple time-of-flight tandem mass spectrometry (LC-QTOF-MS). The parent substance and its pyrolysis products were not detected in urine, while their five metabolites were found. The experiments allowed the location of derivative groups to be established, and thus elucidate rough structures of the metabolites; a dihydroxylated metabolite of UR-144 and mono-, dihydroxylated and carboxylated metabolites of its pyrolysis product were identified.

Emergence and properties of spice and bath salts: a medicinal chemistry perspective

Over the past five years the number of internet sites advertising "legal highs" has literally exploded, as have user reports of experiences (both pleasurable and frightening) with these substances and the number of emergency room visits by users. Although the majority of these "legal highs" have been described as bath salts and herbal extracts, most contain neither plant derived compounds nor components of personal hygiene products. So-called "bath salts" largely contain synthetic analogs of the natural compound Khat; spice-related materials, claimed to be "legal marijuana," are mostly synthetic analogs of cannabinoid receptor ligands that were developed as research tools. This review describes the emergence and properties of these two groups of "legal highs" from a medicinal chemist's perspective.

Distinct pharmacology and metabolism of K2 synthetic cannabinoids compared to Δ(9)-THC: mechanism underlying greater toxicity?

K2 or Spice products are emerging drugs of abuse that contain synthetic cannabinoids (SCBs). Although assumed by many teens and first time drug users to be a "safe" and "legal" alternative to marijuana, many recent reports indicate that SCBs present in K2 produce toxicity not associated with the primary psychoactive component of marijuana, ∆(9)-tetrahydrocannabinol (Δ(9)-THC). This mini-review will summarize recent evidence that use of K2 products poses greater health risks relative to marijuana, and suggest that distinct pharmacological properties and metabolism of SCBs relative to Δ(9)-THC may contribute to the observed toxicity. Studies reviewed will indicate that in contrast to partial agonist properties of Δ(9)-THC typically observed in vitro, SCBs in K2 products act as full cannabinoid receptor type 1 (CB1R) and type 2 (CB2R) agonists in both cellular assays and animal studies. Furthermore, unlike Δ(9)-THC metabolism, several SCB metabolites retain high affinity for, and exhibit a range of intrinsic activities at, CB1 and CB2Rs. Finally, several reports indicate that although quasi-legal SCBs initially evaded detection and legal consequences, these presumed "advantages" have been limited by new legislation and development of product and human testing capabilities. Collectively, evidence reported in this mini-review suggests that K2 products are neither safe nor legal alternatives to marijuana. Instead, enhanced toxicity of K2 products 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 CB2Rs, highlights the inherent danger that may accompany use of these substances.

Moving around the molecule: relationship between chemical structure and in vivo activity of synthetic cannabinoids

Originally synthesized for research purposes, indole- and pyrrole-derived synthetic cannabinoids are the most common psychoactive compounds contained in abused products marketed as "spice" or "herbal incense." While CB1 and CB2 receptor affinities are available for most of these research chemicals, in vivo pharmacological data are sparse. In mice, cannabinoids produce a characteristic profile of dose-dependent effects: antinociception, hypothermia, catalepsy and suppression of locomotion. In combination with receptor binding data, this tetrad battery has been useful in evaluation of the relationship between the structural features of synthetic cannabinoids and their in vivo cannabimimetic activity. Here, published tetrad studies are reviewed and additional in vivo data on synthetic cannabinoids are presented. Overall, the best predictor of likely cannabimimetic effects in the tetrad tests was good CB1 receptor affinity. Further, retention of good CB1 affinity and in vivo activity was observed across a wide array of structural manipulations of substituents of the prototypic aminoalkylindole molecule WIN55,212-2, including substitution of an alkyl for the morpholino group, replacement of an indole core with a pyrrole or phenylpyrrole, substitution of a phenylacetyl or tetramethylcyclopropyl group for JWH-018's naphthoyl, and halogenation of the naphthoyl group. This flexibility of cannabinoid ligand-receptor interactions has been a particular challenge for forensic scientists who have struggled to identify and regulate each new compound as it has appeared on the drug market. One of the most pressing future research needs is determination of the extent to which the pharmacology of these synthetic cannabinoids may differ from those of classical cannabinoids.

First metabolic profile of XLR-11, a novel synthetic cannabinoid, obtained by using human hepatocytes and high-resolution mass spectrometry

BACKGROUND

Since the mid-2000s synthetic cannabinoids have been abused as recreational drugs, prompting scheduling of these substances in many countries. To circumvent legislation, manufacturers constantly market new compounds; [1-(5-fluoropentyl)indol-3-yl]-(2,2,3,3-tetramethylcyclopropyl)methanone (XLR-11), the fluorinated UR-144 analog, is one of the most recent and widely abused drugs, and its use is now linked with acute kidney injury. Our goal was to investigate XLR-11 metabolism for identification of major urinary targets in analytical methods and to clarify the origin of metabolites when one or more parent synthetic cannabinoids can be the source.

METHODS

We incubated 10 μmol/L XLR-11 with pooled human hepatocytes and sampled after 1 and 3 h. Samples were analyzed by high-resolution mass spectrometry with a TOF scan followed by information-dependent acquisition triggered product ion scans with dynamic background subtraction and mass defect filters. Scans were thoroughly data mined with different data processing algorithms (Metabolite Pilot 1.5).

RESULTS

XLR-11 underwent phase I and II metabolism, producing more than 25 metabolites resulting from hydroxylation, carboxylation, hemiketal and hemiacetal formation, internal dehydration, and further glucuronidation of some oxidative metabolites. No sulfate or glutathione conjugation was observed. XLR-11 also was defluorinated, forming UR-144 metabolites. On the basis of mass spectrometry peak areas, we determined that the major metabolites were 2'-carboxy-XLR-11, UR-144 pentanoic acid, 5-hydroxy-UR-144, hydroxy-XLR-11 glucuronides, and 2'-carboxy-UR-144 pentanoic acid. Minor metabolites were combinations of the biotransformations mentioned above, often glucuronidated.

CONCLUSIONS

These are the first data defining major urinary targets of XLR-11 metabolism that could document XLR-11 intake in forensic and clinical investigations.

Identification of novel third-generation synthetic cannabinoids in products by ultra-performance liquid chromatography and time-of-flight mass spectrometry

Synthetic cannabinoids are a group of compounds that are structurally diverse and are commonly found in various herbal incense and potpourri blends, which are sold in convenience stores, smoke shops and over the Internet. During the past few years, multiple state and federal legislations have been enacted controlling various subsets of these compounds that have been detected in compound categories generally considered the first and second product generations. As shown in previous studies, as compounds become controlled, new compounds emerge and become prevalent. We report on the emergence and prevalence of five different compounds (A796,260, MAM-2201, UR-144, URB597 and XLR-11) in the state of Indiana through their qualitative detection in solid-dosage herbal products via rapid solvent extraction and ultra-performance liquid chromatography with time-of-flight mass spectrometry (UPLC/ToF). We demonstrate the use of UPLC/ToF to be a suitable tool in the identification of these substances in a crime laboratory or forensic laboratory setting, which ultimately enables a laboratory to design assays for the detection of specific analytes in biological specimens in regard to regional trends and prevalence.

Cannabinoids in disguise: Δ9-tetrahydrocannabinol-like effects of tetramethylcyclopropyl ketone indoles

Synthetic indole-derived cannabinoids have become commonly used recreational drugs and continue to be abused despite their adverse consequences. As compounds that were identified early in the epidemic (e.g., naphthoylindoles) have become legally banned, new compounds have appeared on the drug market. Two tetramethylcyclopropyl ketone indoles, UR-144 [(1-pentyl-1H-indol-3-yl)-(2,2,3,3-tetramethylcyclopropyl)methanone] and XLR-11 [(1-(5-fluoropentyl)-1H-indol-3-yl)-(2,2,3,3-tetramethylcyclopropyl)methanone], recently have been identified in confiscated products. These compounds are structurally related to a series of CB2-selective compounds explored by Abbott Labs. The purpose of the present study was to evaluate the extent to which UR-144 and XLR-11 shared cannabinoid effects with Δ9-tetrahydrocannabinol (Δ9-THC). Indices of in vitro and in vivo activity at cannabinoid receptors were assessed. Similar to other psychoactive cannabinoid agonists, XLR-11 and UR-144 showed low nanomolar (<30) affinity for CB1 and CB2 receptors, activated these receptors as full agonists, and produced dose-dependent effects that were blocked by rimonabant in mice, including antinociception, hypothermia, catalepsy and suppression of locomotor activity. The potency of both compounds was several-fold greater than Δ9-THC. XLR-11 and UR-144 also substituted for Δ9-THC in a Δ9-THC discrimination procedure in mice, effects that were attenuated by rimonabant. Analysis of urine from mice treated with the compounds revealed that both were extensively metabolized, with predominant urinary excretion as glucuronide conjugates. Together, these results demonstrate that UR-144 and XLR-11 share a pharmacological profile of in vitro and in vivo effects with Δ9-THC and other abused indole-derived cannabinoids and would be predicted to produce Δ9-THC-like subjective effects in humans.

The synthesis and pharmacological evaluation of adamantane-derived indoles: cannabimimetic drugs of abuse

Two novel adamantane derivatives, adamantan-1-yl(1-pentyl-1H-indol-3-yl)methanone (AB-001) and N-(adamtan-1-yl)-1-pentyl-1H-indole-3-carboxamide (SDB-001), were recently identified as cannabimimetic indoles of abuse. Conflicting anecdotal reports of the psychoactivity of AB-001 in humans, and a complete dearth of information about the bioactivity of SDB-001, prompted the preparation of AB-001, SDB-001, and several analogues intended to explore preliminary structure-activity relationships within this class. This study sought to elucidate which structural features of AB-001, SDB-001, and their analogues govern the cannabimimetic potency of these chemotypes in vitro and in vivo. All compounds showed similar full agonist profiles at CB1 (EC50 = 16-43 nM) and CB2 (EC50 = 29-216 nM) receptors in vitro using a FLIPR membrane potential assay, with the exception of SDB-002, which demonstrated partial agonist activity at CB2 receptors. The activity of AB-001, AB-002, and SDB-001 in rats was compared to that of Δ(9)-tetrahydrocannabinol (Δ(9)-THC) and cannabimimetic indole JWH-018 using biotelemetry. SDB-001 dose-dependently induced hypothermia and reduced heart rate (maximal dose 10 mg/kg) with potency comparable to that of Δ(9)-tetrahydrocannabinol (Δ(9)-THC, maximal dose 10 mg/kg), and lower than that of JWH-018 (maximal dose 3 mg/kg). Additionally, the changes in body temperature and heart rate affected by SDB-001 are of longer duration than those of Δ(9)-THC or JWH-018, suggesting a different pharmacokinetic profile. In contrast, AB-001, and its homologue, AB-002, did not produce significant hypothermic and bradycardic effects, even at relatively higher doses (up to 30 mg/kg), indicating greatly reduced potency compared to Δ(9)-THC, JWH-018, and SDB-001.

Contributions of academic laboratories to the discovery and development of chemical biology tools

The academic setting provides an environment that may foster success in the discovery of certain types of small molecule tools while proving less suitable in others. For example, small molecule probes for poorly understood systems, those that exploit a specific resident expertise, and those whose commercial return is not apparent are ideally suited to be pursued in a university setting. In this review, we highlight five projects that emanated from academic research groups and generated valuable tool compounds that have been used to interrogate biological phenomena: reactive oxygen species (ROS) sensors, GPR30 agonists and antagonists, selective CB2 agonists, Hsp70 modulators, and β-amyloid PET imaging agents. By taking advantage of the unique expertise resident in university settings and the ability to pursue novel projects that may have great scientific value but with limited or no immediate commercial value, probes from academic research groups continue to provide useful tools and generate a long-term resource for biomedical researchers.

Identification and quantification of synthetic cannabinoids in 'spice-like' herbal mixtures: a snapshot of the German situation in the autumn of 2012

Synthetic compounds mimicking cannabis-like effects are a recent trend. Currently, these so-called synthetic cannabinoids are the largest and fastest growing class of newly appearing designer drugs. Many national authorities are continuously adapting their regulations to keep pace with the permanently changing variety of compounds. We have analyzed eight herbal smoking blends containing synthetic cannabinoids. Altogether, nine compounds could be identified, namely AM-2201, AM-2201-pMe (MAM-2201), AM-1220, AM-1220-azepane, UR-144, XLR-11, JWH-122-pentenyl, AM-2232, and STS-135. Newly appearing compounds were isolated by column chromatography and their structures elucidated by 1D- and 2D-nuclear magnetic resonance (NMR) experiments. In addition, the compounds were investigated by electron ionization-mass spectrometry (EI-MS) and electrospray ionization-tandem mass spectrometry (ESI-MS/MS) to complete the physicochemical dataset. Based on the purified compounds a universal gas chromatography-mass spectrometry (GC-MS) method was developed for the identification and quantification of these compounds in commercial smoking blends. By applying this method, up to five different compounds could be found in such products showing total concentrations from 72 to 303 mg/g smoking blend while individual compounds ranged from 0.4 to 303 mg/g. (1)H NMR spectra of the chiral compounds AM-1220 and its azepane-isomer recorded in the presence of 1 equivalent of (R)-(+)-α-methoxy-α-trifluoromethylphenylacetic acid (MTPA, Mosher's acid) showed them to be racemic mixtures.

Gas and liquid chromatography-mass spectrometry detection of the urinary metabolites of UR-144 and its major pyrolysis product

Studies on the pyrolysis of the synthetic cannabinoid agonist UR-144 ((1-pentyl-1H-indol-3-yl)(2,2,3,3-tetramethylcyclopropyl)methanone) have shown that its major pyrolysis product is a tetramethylcyclopropane ring-opened alkene. Considering that smoking is a common way of ingesting synthetic cannabimimetics, the presence of the metabolites of this pyrolysis product would be expected in biological fluids. Using GC-MS and LC-MS-MS methods, a series of phase I metabolites of UR-144 and its pyrolysis product were detected in the urine samples from patients admitted to hospital with suspected drug intoxication. The metabolites were tentatively identified as the products of mono-hydroxylation, di-hydroxylation, mono-hydroxylation with formation of the carbonyl group on the N-alkyl chain, carboxylation and N-dealkylation with mono-hydroxylation. In the case of the UR-144 pyrolysis product, metabolites with hydration of the aliphatic double bond were also identified. The parent compounds were detected as trace amounts in some urine samples, and the hydrated derivative of the UR-144 pyrolysis product was detected in the majority of samples. The detection of mono-hydroxylated metabolites of UR-144 (LC-MS-MS) and mono-hydroxylated/with hydration metabolites of the UR-144 pyrolysis product (GC-MS) was found to be the most useful method of establishing UR-144 ingestion.

Selective CB2 agonists with anti-pruritic activity: discovery of potent and orally available bicyclic 2-pyridones

The CB2 receptor has emerged as a potential target for the treatment of pruritus as well as pain without CB1-mediated side effects. We previously identified 2-pyridone derivatives 1 and 2 as potent CB2 agonists; however, this series of compounds was found to have unacceptable pharmacokinetic profiles with no significant effect in vivo. To improve these profiles, we performed further structural optimization of 1 and 2, which led to the discovery of bicyclic 2-pyridone 18e with improved CB2 affinity and selectivity over CB1. In a mouse pruritus model, 18e inhibited compound 48/80 induced scratching behavior at a dose of 100 mg/kg. In addition, the docking model of 18e with an active-state CB2 homology model indicated the structural basis of its high affinity and selectivity over CB1.

Development and preliminary validation of a plate-based CB1/CB2 receptor functional assay

Cannabinoid (CB) receptors are being targeted therapeutically for the treatment of anxiety, obesity, movement disorders, glaucoma, and pain. More recently, cannabinoid agonists have displayed antiproliferative activity against breast cancer and prostate cancer in animal models. To study cannabinoid receptor ligands, we have developed a novel plate-based assay that measures internalization of CB1/CB2 receptors by determining the change in the intracellular levels of the radiolabeled agonists: [(3)H]Win55-212-2 for CB1 and [(3)H]CP55-940 for CB2. The developed plate-based assay was validated by determining IC50 values for known antagonists: AM251, AM281, AM630, and AM6545. The data obtained were consistent with previously reported values, thereby confirming that the assay can be used to determine the functional binding activities (IC50) of antagonists for the CB1 and CB2 receptors. In addition, we demonstrated that the plate-based assay may be used for screening against complex matrices. Specifically, we demonstrated that the plate-based assay was able to identify which extracts of several species of the genus Zanthoxylum had activity at the CB1/CB2 receptors.

Design, synthesis, and binding mode prediction of 2-pyridone-based selective CB2 receptor agonists

Selective CB2 agonists have the potential for treating pain without central CB1-mediated adverse effects. Screening efforts identified 1,2-dihydro-3-isoquinolone 1; however, this compound has the drawbacks of being difficult to synthesize with two asymmetric carbons on an isoquinolone scaffold and of having a highly lipophilic physicochemical property. To address these two major problems, we designed the 2-pyridone-based lead 15a, which showed moderate affinity for CB2. Optimization of 15a led to identification of 39f with high affinity for CB2 and selectivity over CB1. Prediction of the binding mode of 39f in complex with an active-state CB2 homology model provided structural insights into its high affinity for CB2.