Prospective therapeutic agents for obesity: Molecular modification approaches of centrally and peripherally acting selective cannabinoid 1 receptor antagonists

Seven-membered N-heterocycles as approved drugs and promising leads in medicinal chemistry as well as the metal-free domino access to their scaffolds

Azepanes or azepines are structural motifs of many drugs, drug candidates and evaluated lead compounds. Even though compounds having N-heterocyclic 7-membered rings are often found in nature (e.g. alkaloids), the natural compounds of this group are rather rare as approved therapeutics. Thus, recently studied and approved azepane or azepine-congeners predominantly consist of semi-synthetically or synthetically-obtained scaffolds. In this review a comparison of approved drugs and recently investigated leads was proposed taking into regard their structural aspects (stereochemistry), biological activities, pharmacokinetic properties and confirmed molecular targets. The 7-membered N-heterocycles reveal a wide range of biological activities, not only against CNS diseases, but also as e.g. antibacterial, anticancer, antiviral, antiparasitic and against allergy agents. As most of the approved or investigated potential drugs or lead structures, belonging to 7-membered N-heterocycles, are synthetic scaffolds, this report also reveals different and efficient metal-free cascade approaches useful to synthesize both simple azepane or azepine-containing congeners and those of oligocyclic structures. Stereochemistry of azepane/azepine fused systems, in view of biological data and binding with the targets, is discussed. Apart from the approved drugs, we compare advances in SAR studies of 7-membered N-heterocycles (mainly from 2018 to 2023), whereas the related synthetic part concerning various domino strategies is focused on the last ten years.

Pharmacological Evaluation of Cannabinoid Receptor Modulators Using GRABeCB2.0 Sensor

Cannabinoid receptors CB1R and CB2R are G-protein coupled receptors acted upon by endocannabinoids (eCBs), namely 2-arachidonoylglycerol (2-AG) and N-arachidonoyl ethanolamine (AEA), with unique pharmacology and modulate disparate physiological processes. A genetically encoded GPCR activation-based sensor that was developed recently-GRABeCB2.0-has been shown to be capable of monitoring real-time changes in eCB levels in cultured cells and preclinical models. However, its responsiveness to exogenous synthetic cannabinoid agents, particularly antagonists and allosteric modulators, has not been extensively characterized. This current study expands upon the pharmacological characteristics of GRABeCB2.0 to enhance the understanding of fluorescent signal alterations in response to various functionally indiscriminate cannabinoid ligands. The results from this study could enhance the utility of the GRABeCB2.0 sensor for in vitro as well as in vivo studies of cannabinoid action and may aid in the development of novel ligands.

The intervention of cannabinoid receptor in chronic and acute kidney disease animal models: a systematic review and meta-analysis

AIM

Cannabinoid receptors are components of the endocannabinoid system that affect various physiological functions. We aim to investigate the effect of cannabinoid receptor modulation on kidney disease.

METHODS

PubMed, Web of Science databases, and EMBASE were searched. Articles selection, data extraction and quality assessment were independently performed by two investigators. The SYRCLE's RoB tool was used to assess the risk of study bias, and pooled SMD using a random-effect model and 95% CIs were calculated. Subgroup analyses were conducted in preselected subgroups, and publication bias was evaluated. We compared the effects of CB1 and CB2 antagonists and/or knockout and agonists and/or genetic regulation on renal function, blood glucose levels, body weight, and pathological damage-related indicators in different models of chronic and acute kidney injury.

RESULTS

The blockade or knockout of CB1 could significantly reduce blood urea nitrogen [SMD,- 1.67 (95% CI - 2.27 to - 1.07)], serum creatinine [SMD, - 1.88 (95% CI - 2.91 to - 0.85)], and albuminuria [SMD, - 1.60 (95% CI - 2.16 to - 1.04)] in renal dysfunction animals compared with the control group. The activation of CB2 group could significantly reduce serum creatinine [SMD, - 0.97 (95% CI - 1.83 to - 0.11)] and albuminuria [SMD, - 2.43 (95% CI - 4.63 to - 0.23)] in renal dysfunction animals compared with the control group.

CONCLUSIONS

The results suggest that targeting cannabinoid receptors, particularly CB1 antagonists and CB2 agonists, can improve kidney function and reduce inflammatory responses, exerting a renal protective effect and maintaining therapeutic potential in various types of kidney disease.

Correlation intensity index-index of ideality of correlation: A hyphenated target function for furtherance of MAO-B inhibitory activity assessment

Monoamine oxidases are the enzymes involved in the management of brain homeostasis through oxidative deamination of monoamines such as neurotransmitters, tyramine etc. The excessive production of monoamine oxidase-B specifically results in numerous neurodegenerative disorders like Alzheimer's and Parkinson's diseases. Inhibitors of monoamine oxidase-B are applied in the management of these disorders. Here in this article we have developed robust hybrid descriptor based QSAR models related to 123 monoamine oxidase-B inhibitors through CORAL software by means of Monte Carlo optimization method. Three target functions were applied to prepare QSAR models and three splits were made for each target function. The most reliable, robust and better predictive QSAR models were developed with TF3 (correlation intensity index -index of ideality of correlation). Correlation intensity index showed positive effect on QSAR models. The structural features obtained from the QSAR modeling were incorporated in newly designed molecules and exhibited positive effect on their endpoint. Significant binding interactions were represented by these molecules in docking studies. Molecule B5 displayed prominent pIC50 (8.3) and binding affinity (-11.5 kcal mol-1) towards monoamine oxidase-B.

Cannabinoformins: Designing Biguanide-Embedded, Orally Available, Peripherally Selective Cannabinoid-1 Receptor Antagonists for Metabolic Syndrome Disorders

We have designed orally bioavailable, non-brain-penetrant antagonists of the cannabinoid-1 receptor (CB1R) with a built-in biguanide sensor to mimic 5'-adenosine monophosphate kinase (AMPK) activation for treating obesity-associated co-morbidities. A series of 3,4-diarylpyrazolines bearing rational pharmacophoric pendants designed to limit brain penetration were synthesized and evaluated in CB1R ligand binding assays and recombinant AMPK assays. The compounds displayed high CB1R binding affinity and potent CB1R antagonist activities and acted as AMPK activators. Select compounds showed good oral exposure, with compounds 36, 38-S, and 39-S showing <5% brain penetrance, attesting to peripheral restriction. In vivo studies of 38-S revealed decreased food intake and body weight reduction in diet-induced obese mice as well as oral in vivo efficacy of 38-S in ameliorating glucose tolerance and insulin resistance. The designed "cannabinoformin" four-arm CB1R antagonists could serve as potential leads for treatment of metabolic syndrome disorders with negligible neuropsychiatric side effects.

Exploring the Therapeutic Potential of Cannabinoid Receptor Antagonists in Inflammation, Diabetes Mellitus, and Obesity

Recently, research has greatly expanded the knowledge of the endocannabinoid system (ECS) and its involvement in several therapeutic applications. Cannabinoid receptors (CBRs) are present in nearly every mammalian tissue, performing a vital role in different physiological processes (neuronal development, immune modulation, energy homeostasis). The ECS has an essential role in metabolic control and lipid signaling, making it a potential target for managing conditions such as obesity and diabetes. Its malfunction is closely linked to these pathological conditions. Additionally, the immunomodulatory function of the ECS presents a promising avenue for developing new treatments for various types of acute and chronic inflammatory conditions. Preclinical investigations using peripherally restricted CBR antagonists that do not cross the BBB have shown promise for the treatment of obesity and metabolic diseases, highlighting the importance of continuing efforts to discover novel molecules with superior safety profiles. The purpose of this review is to examine the roles of CB1R and CB2Rs, as well as their antagonists, in relation to the above-mentioned disorders.

Regiocontrolled Synthesis of 1-Substituted-3(5)-carboxyalkyl-1H-pyrazoles Using Trichloromethyl Enones

In this work, we present a regiocontrolled methodology to prepare 1-substituted-3(5)-carboxyalkyl-1H-pyrazoles using trichloromethyl enones as starting materials. It was found that the selectivity of the reaction depends on the nature of the hydrazine: when using arylhydrazine hydrochlorides, synthesis of the 1,3-regioisomer was achieved (22 examples, 37-97% yields), while the corresponding free hydrazine led exclusively to the 1,5-regioisomer (12 examples, 52-83% yields). The trichloromethyl group was used as a precursor for the carboxyalkyl moiety, furnishing a one-pot three-component regioselective protocol suitable for preparing both isomers at moderate to excellent yields. The selectivity of the reaction was investigated through NMR analyses and the structures of the products were unambiguously determined by SCXR analyses.

Oral Ionic Liquid for Transdermal Delivery and Obesity Treatment

Obesity is currently a prerequisite for more than 70% of adults, including chronic obesity and long-term obesity. With the increase of diabetes patients in the world, it is urgent to develop effective oral drugs to replace insulin. However, the gastrointestinal tract is a main obstacle to oral drug preparations. Here, a highly effective oral drug was developed, mainly formulated as an ionic liquid (IL) prepared by l-(-)-carnitine and geranic acid. Density functional theory (DFT) calculations showed that l-(-)-carnitine and geranic acid can exist stably through hydrogen bonding. IL can significantly enhance the transdermal transport of drugs. In vitro study of intestinal permeability showed that particles formed by IL can prevent the absorption of intestinal fat. Compared with the control group, oral administration of IL (10 mL kg^-1) significantly reduced blood glucose, white adipose tissue in the liver and epididymis, and the expression of SREBP-1c and ACC in IL. Therefore, these results and high-throughput sequencing analysis showed that IL can effectively reduce the intestinal absorption of adipose tissue to reduce blood glucose. IL has good biocompatibility and stability. Therefore, IL has a certain application value in the field of oral drug-delivery carriers, which provides an effective means for the treatment of diabetes and is a potential tool to solve the epidemic of obesity.

Endocannabinoid System: Chemical Characteristics and Biological Activity

The endocannabinoid system (eCB) has been studied to identify the molecular structures present in Cannabis sativa. eCB consists of cannabinoid receptors, endogenous ligands, and the associated enzymatic apparatus responsible for maintaining energy homeostasis and cognitive processes. Several physiological effects of cannabinoids are exerted through interactions with various receptors, such as CB1 and CB2 receptors, vanilloid receptors, and the recently discovered G-protein-coupled receptors (GPR55, GPR3, GPR6, GPR12, and GPR19). Anandamide (AEA) and 2-arachidoylglycerol (2-AG), two small lipids derived from arachidonic acid, showed high-affinity binding to both CB1 and CB2 receptors. eCB plays a critical role in chronic pain and mood disorders and has been extensively studied because of its wide therapeutic potential and because it is a promising target for the development of new drugs. Phytocannabinoids and synthetic cannabinoids have shown varied affinities for eCB and are relevant to the treatment of several neurological diseases. This review provides a description of eCB components and discusses how phytocannabinoids and other exogenous compounds may regulate the eCB balance. Furthermore, we show the hypo- or hyperfunctionality of eCB in the body and how eCB is related to chronic pain and mood disorders, even with integrative and complementary health practices (ICHP) harmonizing the eCB.

Phytocannabinoid Pharmacology: Medicinal Properties of Cannabis sativa Constituents Aside from the "Big Two"

Plant-based therapies date back centuries. Cannabis sativa is one such plant that was used medicinally up until the early part of the 20th century. Although rich in diverse and interesting phytochemicals, cannabis was largely ignored by the modern scientific community due to its designation as a schedule 1 narcotic and restrictions on access for research purposes. There was renewed interest in the early 1990s when the endocannabinoid system (ECS) was discovered, a complex network of signaling pathways responsible for physiological homeostasis. Two key components of the ECS, cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2), were identified as the molecular targets of the phytocannabinoid Δ⁹-tetrahydrocannabinol (Δ⁹-THC). Restrictions on access to cannabis have eased worldwide, leading to a resurgence in interest in the therapeutic potential of cannabis. Much of the focus has been on the two major constituents, Δ⁹-THC and cannabidiol (CBD). Cannabis contains over 140 phytocannabinoids, although only a handful have been tested for pharmacological activity. Many of these minor cannabinoids potently modulate receptors, ionotropic channels, and enzymes associated with the ECS and show therapeutic potential individually or synergistically with other phytocannabinoids. The following review will focus on the pharmacological developments of the next generation of phytocannabinoid therapeutics.

New cannabinoid receptor antagonists as pharmacological tool

Synthesis and pharmacological evaluation of a new series of cannabinoid receptor antagonists of indazole ether derivatives have been performed. Pharmacological evaluation includes radioligand binding assays with [³H]-CP55940 for CB1 and CB2 receptors and functional activity for cannabinoid receptors on isolated tissue. In addition, functional activity of the two synthetic cannabinoids antagonists 18 (PGN36) and 17 (PGN38) were carried out in the osteoblastic cell line MC3T3-E1 that is able to express CB2R upon osteogenic conditions. Both antagonists abolished the increase in collagen type I gene expression by the well-known inducer of bone activity, the HU308 agonist. The results of pharmacological tests have revealed that four of these derivatives behave as CB2R cannabinoid antagonists. In particular, the compounds 17 (PGN38) and 18 (PGN36) highlight as promising candidates as pharmacological tools.

Overview of recent developments of pyrazole derivatives as an anticancer agent in different cell line

Pyrazole is a five-membered aromatic heterocyclic ring with two adjacent nitrogen atoms C₃H₃N₂H.The presence of this nucleus in pharmacological agents of various therapeutic categories gifts a broad spectrum of biological activities and pharmaceuticals that contain pyrazole like celecoxib (anti-inflammatory), CDPPB (antipsychotic), Rimonabant (anti-obesity), Difenamizole, (Analgesic), Betazole (H2 receptor agonist), Fezolamide (Antidepressant), etc… The pharmacological potential of the pyrazole fraction is proved in many publication where they synthesized and evaluated pyrazoles against several biological agents. The aim of this article review is to survey recent works linking pyrazole structures to anticancer activities corresponding to 9 different type of cancer.

Oral ionic liquid for the treatment of diet-induced obesity

More than 70% of American adults are overweight or obese, a precondition leading to chronic diseases, including diabetes and hypertension. Among other factors, diets with high fat and carbohydrate content have been implicated in obesity. In this study, we hypothesize that the choline and geranate (CAGE) ionic liquid can reduce body weight by decreasing fat absorption through the intestine. In vitro studies performed using docosahexaenoic acid (DHA), a model fat molecule, show that CAGE forms particles 2 to 4 μm in diameter in the presence of fat molecules. Ex vivo permeation studies in rat intestine showed that formation of such large particles reduces intestinal fat absorption. In vivo, CAGE reduces DHA absorption by 60% to 70% compared with controls. DHA administered with CAGE was retained in the intestine even after 6 h. Rats fed with a high-fat diet (HFD) and 10 μL of daily oral CAGE exhibited 12% less body weight gain compared with rats fed with an HFD without CAGE for 30 d. Rats that were given CAGE also ate less food than the control groups. Serum biochemistry and histology results indicated that CAGE was well tolerated by the rats. Collectively, our data support the hypothesis that CAGE interacts with fat molecules to prevent their absorption through intestinal tissue and potentially providing a feeling of satiety. We conclude that CAGE offers an effective means to control body weight and a promising tool to tackle the obesity epidemic.

Directed C-H Halogenation Reactions Catalysed by PdII Supported on Polymers under Batch and Continuous Flow Conditions

A new generation of N-heterocyclic carbene palladium(II) complexes containing vinyl groups in different positions in the backbone of the N-heterocycle have been developed. The fully characterised monomers were copolymerised with divinylbenzene to fabricate robust polymer supported NHC-Pd^II complexes and these polymers were applied as heterogeneous catalysts in directed C-H halogenation of arenes with a pyridine-type directing group. The catalysts demonstrated medium-high catalytic activity with up to 90 % conversion and 100 % selectivity in chlorination. They are heterogeneous and recyclable (at least six times) with no significant leaching of palladium in batch mode catalysis. The best catalyst was also applied under continuous flow conditions where it disclosed an exceptional activity (90 % conversion) and 100 % selectivity for the mono-halogenated product for at least six days, with no leaching of palladium, no loss of activity and an ability to maintain the original oxidation state of Pd^II .

Innovative Therapeutic Potential of Cannabinoid Receptors as Targets in Alzheimer’s Disease and Less Well-Known Diseases

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The discovery of cannabinoid receptors at the beginning of the 1990s, CB1 cloned in 1990 and CB2 cloned in 1993, and the availability of selective and potent cannabimimetics could only be justified by the existence of endogenous ligands that are capable of binding to them. Thus, the characterisation and cloning of the first cannabinoid receptor (CB1) led to the isolation and characterisation of the first endocannabinoid, arachidonoylethanolamide (AEA), two years later and the subsequent identification of a family of lipid transmitters known as the fatty acid ester 2-arachidonoylglycerol (2-AG).

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The endogenous cannabinoid system is a complex signalling system that comprises transmembrane endocannabinoid receptors, their endogenous ligands (the endocannabinoids), the specific uptake mechanisms and the enzymatic systems related to their biosynthesis and degradation.

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The endocannabinoid system has been implicated in a wide diversity of biological processes, in both the central and peripheral nervous systems, including memory, learning, neuronal development, stress and emotions, food intake, energy regulation, peripheral metabolism, and the regulation of hormonal balance through the endocrine system.

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In this context, this article will review the current knowledge of the therapeutic potential of cannabinoid receptor as a target in Alzheimer’s disease and other less well-known diseases that include, among others, multiple sclerosis, bone metabolism, and Fragile X syndrome.

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The therapeutic applications will be addressed through the study of cannabinoid agonists acting as single drugs and multi-target drugs highlighting the CB2 receptor agonist.

Functionalized 6-(piperidin-1-yl)-8,9-diphenyl purines as inverse agonists of the CB1 receptor - SAR efforts towards selectivity and peripheralization

Antagonists of type 1 cannabinoid receptors (CB1) may be useful in treating diabetes, hepatic disorders, and fibrosis. Otenabant (1) is a potent and selective CB1 inverse agonist that was under investigation as an anti-obesity agent, but its development was halted once adverse effects associated with another marketed inverse agonist rimonabant (2) became known. Non-tissue selective antagonists of CB1 that have high levels of brain penetration produce adverse effects in a small subset of patients including anxiety, depression and suicidal ideation. Currently, efforts are underway to produce compounds that have limited brain penetration. In this report, novel analogs of 1 are explored to develop and test strategies for peripheralization. The piperidine of 1 is studied as a linker, which is functionalized with alkyl, heteroalkyl, aryl and heteroaryl groups using a connector in the form of an amine, amide, sulfonamide, sulfamide, carbamate, oxime, amidine, or guanidine. We also report more polar replacements for the 4-chlorophenyl group in the 9-position of the purine core, which improve calculated physical properties of the molecules. These studies resulted in compounds such as 75 that are potent inverse agonists of hCB1 with exceptional selectivity for hCB1 over hCB2. SAR studies revealed ways to adjust physical properties to limit brain exposure.

Functionalized 6-(Piperidin-1-yl)-8,9-Diphenyl Purines as Peripherally Restricted Inverse Agonists of the CB1 Receptor

Peripherally restricted CB1 receptor antagonists may be useful in treating metabolic syndrome, diabetes, liver diseases, and gastrointestinal disorders. Clinical development of the centrally acting CB1 inverse agonist otenabant (1) was halted due to its potential of producing adverse effects. SAR studies of 1 are reported herein with the objective of producing peripherally restricted analogues. Crystal structures of hCB1 and docking studies with 1 indicate that the piperidine group could be functionalized at the 4-position to access a binding pocket that can accommodate both polar and nonpolar groups. The piperidine is studied as a linker, functionalized with alkyl, heteroalkyl, aryl, and heteroaryl groups using a urea connector. Orally bioavailable and peripherally selective compounds have been produced that are potent inverse agonists of hCB1 with exceptional selectivity for hCB1 over hCB2. Compound 38 blocked alcohol-induced liver steatosis in mice and has good ADME properties for further development.

Cannabis: From a Plant That Modulates Feeding Behaviors toward Developing Selective Inhibitors of the Peripheral Endocannabinoid System for the Treatment of Obesity and Metabolic Syndrome

In this review, we discuss the role of the endocannabinoid (eCB) system in regulating energy and metabolic homeostasis. Endocannabinoids, via activating the cannabinoid type-1 receptor (CB₁R), are commonly known as mediators of the thrifty phenotype hypothesis due to their activity in the central nervous system, which in turn regulates food intake and underlies the development of metabolic syndrome. Indeed, these findings led to the clinical testing of globally acting CB₁R blockers for obesity and various metabolic complications. However, their therapeutic potential was halted due to centrally mediated adverse effects. Recent observations that highlighted the key role of the peripheral eCB system in metabolic regulation led to the preclinical development of various novel compounds that block CB₁R only in peripheral organs with very limited brain penetration and without causing behavioral side effects. These unique molecules, which effectively ameliorate obesity, type II diabetes, fatty liver, insulin resistance, and chronic kidney disease in several animal models, are likely to be further developed in the clinic and may revive the therapeutic potential of blocking CB₁R once again.

A patent update on cannabinoid receptor 1 antagonists (2015-2018)

INTRODUCTION

The endocannabinoid system is an important regulator of various physiological processes. Preclinical and clinical studies indicate that attenuation of the endocannabinoid system via antagonism of the type 1 cannabinoid receptor (CB1) is an excellent strategy to treat obesity, metabolic syndrome and associated disorders. However, centrally acting antagonists of CB1 also produce adverse effects like depression and anxiety. Current efforts are geared towards discovery and optimization of antagonists and modulators of CB1 that have limited brain penetration.

AREAS COVERED

Several recent publications and patent applications support the development of peripherally acting CB1 receptor antagonists and modulators. In this review, recent patents and applications (2015-2018) are summarized and discussed.

EXPERT OPINION

Approximately 30 new inventions have been reported since 2015, along with 3 recent commercial deals, highlighting the importance of this class of therapeutics. Taken together, peripherally acting CB1 receptor antagonists and modulators are an emerging class of drugs for metabolic syndrome, non-alcoholic steatohepatitis (NASH) and other important disorders where this receptor has been implicated.

Role of the endocannabinoid system in drug addiction

Drug addiction is a chronic relapsing disorder that produces a dramaticglobal health burden worldwide. Not effective treatment of drug addiction is currently available probably due to the difficulties to find an appropriate target to manage this complex disease raising the needs for further identification of novel therapeutic approaches. The endocannabinoid system has been found to play a crucial role in the neurobiological substrate underlying drug addiction. Endocannabinoids and cannabinoid receptors are widely expressed in the main areas of the mesocorticolimbic system that participate in the initiation and maintenance of drug consumption and in the development of compulsion and loss of behavioral control occurring during drug addiction. The identification of the important role played by CB1 cannabinoid receptors in drug addiction encouraged the possible used of an early commercialized CB1 receptor antagonist for treating drug addiction. However, the incidence of serious psychiatric adverse events leaded to the sudden withdrawal from the market of this CB1 antagonist and all the research programs developed by pharmaceutical companies to obtain new CB1 antagonists were stopped. Currently, new research strategies are under development to target the endocannabinoid system for drug addiction avoiding these side effects, which include allosteric negative modulators of CB1 receptors and compounds targeting CB2 receptors. Recent studies showing the potential role of CB2 receptors in the addictive properties of different drugs of abuse have open a promising research opportunity to develop novel possible therapeutic approaches.

Role for fatty acid amide hydrolase (FAAH) in the leptin-mediated effects on feeding and energy balance

Endocannabinoid signaling regulates feeding and metabolic processes and has been linked to obesity development. Several hormonal signals, such as glucocorticoids and ghrelin, regulate feeding and metabolism by engaging the endocannabinoid system. Similarly, studies have suggested that leptin interacts with the endocannabinoid system, yet the mechanism and functional relevance of this interaction remain elusive. Therefore, we explored the interaction between leptin and endocannabinoid signaling with a focus on fatty acid amide hydrolase (FAAH), the primary degradative enzyme for the endocannabinoid N-arachidonoylethanolamine (anandamide; AEA). Mice deficient in leptin exhibited elevated hypothalamic AEA levels and reductions in FAAH activity while leptin administration to WT mice reduced AEA content and increased FAAH activity. Following high fat diet exposure, mice developed resistance to the effects of leptin administration on hypothalamic AEA content and FAAH activity. At a functional level, pharmacological inhibition of FAAH was sufficient to prevent leptin-mediated effects on body weight and food intake. Using a novel knock-in mouse model recapitulating a common human polymorphism (FAAH C385A; rs324420), which reduces FAAH activity, we investigated whether human genetic variance in FAAH affects leptin sensitivity. While WT (CC) mice were sensitive to leptin-induced reductions in food intake and body weight gain, low-expressing FAAH (AA) mice were unresponsive. These data demonstrate that FAAH activity is required for leptin's hypophagic effects and, at a translational level, suggest that a genetic variant in the FAAH gene contributes to differences in leptin sensitivity in human populations.

Peripheral CB1 Receptor Neutral Antagonist, AM6545, Ameliorates Hypometabolic Obesity and Improves Adipokine Secretion in Monosodium Glutamate Induced Obese Mice

Effect of peripheral cannabinoid receptor 1 (CB1R) blockade by AM6545 in the monosodium glutamate (MSG)-induced hypometabolic and hypothalamic obesity was observed, and the impact on intraperitoneal adipose tissue and adipokines was investigated. The MSG mice is characterized by excessive abdominal obesity, and combined with dyslipidemia and insulin resistance. 3-Week AM6545 treatment dose-dependently decreased the body weight, intraperitoneal fat mass, and rectified the accompanied dyslipidemia include elevated serum triglyceride, total cholesterol, free fatty acids, and lowered LDLc level. Glucose intolerance and hyperinsulinemia were also alleviated. But AM6545 didn’t affect the food-intake consistently through the experiment. In line with the reduction on fat mass, the size of adipocyte was reduced markedly. Most interestingly, AM6545 showed significant improvement on levels of circulating adipokines including lowering leptin, asprosin and TNFα, and increasing HMW adiponectin. Correspondingly, dysregulated gene expression of lipogenesis, lipolysis, and adipokines in the adipose tissue were nearly recovered to normal level after AM6545 treatment. Additionally, western blot analysis revealed that AM6545 corrected the elevated CB1R and PPARγ protein expression, while increased the key energy uncoupling protein UCP1 expression in adipose tissue. Taken together, the current study indicates that AM6545 induced a comprehensive metabolic improvement in the MSG mice including counteracting the hypometabolic and hypothalamic obesity, and improving the accompanied dyslipidemia and insulin resistance. One key underlying mechanism is related to ameliorate on the metabolic deregulation of adipose tissue, the synthesis and secretion of adipokines were thus rectified, and finally the catabolism was increased and the anabolism was reduced in intraperitoneal adipose tissue. Findings from this study will provide the valuable information about peripheral CB1R antagonist in managing hypometabolic obesity.

New role of phenothiazine derivatives as peripherally acting CB1 receptor antagonizing anti-obesity agents

Developing peripherally active cannabinoid 1 (CB1) receptor antagonists is a novel therapeutic approach for the management of obesity. An unusual phenothiazine scaffold containing CB1R antagonizing hit was identified by adopting virtual screening work flow. The hit so identified was further modified by introducing polar functional groups into it to enhance the polar surface area and decrease the hydrophobicity of the resulting molecules. CB1 receptor antagonistic activity for the designed compounds was computed by the previously established pharmacophore and three dimensional quantitative structure-activity relationship models. Docking studies of these designed compounds confirmed the existence of favourable interactions within the active site of the CB1 receptor. The designed compounds were synthesized and evaluated for their CB1 receptor antagonistic activity. Parallel artificial membrane permeability assay was performed to evaluate their potential to permeate into the central nervous system wherein it was observed that the compounds did not possess the propensity to cross the blood brain barrier and would be devoid of central nervous system side effects. In pharmacological evaluation, the synthesized compounds (23, 25, 27 and 34) showed significant decrease in food intake suggesting their potential application in the management of obesity through CB1 receptor antagonist activity.

Novel Peripherally Restricted Cannabinoid 1 Receptor Selective Antagonist TXX-522 with Prominent Weight-Loss Efficacy in Diet Induced Obese Mice

The clinical development of the first generation of globally active cannabinoid 1 receptor (CB1R) antagonists was suspended because of their adverse neuropsychiatric effects. Selective blockade of peripheral CB1Rs has the potential to provide a viable strategy for the treatment of severe obesity while avoiding these central nervous system side effects. In the current study, a novel compound (TXX-522) was rationally designed based on the parent nucleus of a classical CB1R-selective antagonist/inverse agonist, rimonabant (SR141716A). Docking assays indicate that TXX-522 was bound with the CB1R in a mode similar to that of SR141716A. TXX-522 showed good binding, CB1R-selectivity (over the CB2R), and functional antagonist activities in a range of in vitro molecular and cellular assays. In vivo analysis of the steady state distribution of TXX-522 in the rat brain and blood tissues and the assay of its functional effects on CB1R activity collectively showed that TXX-522 showed minimal brain penetration. Moreover, the in vivo pharmacodynamic study further revealed that TXX-522 had good oral bioavailability and a potent anti-obesity effect, and ameliorated insulin resistance in high-fat diet-induced obese mice. No impact on food intake was observed in this model, confirming the limited brain penetration of this compound. Thus, the current study indicates that TXX-522 is a novel and potent peripherally acting selective CB1R antagonist with the potential to control obesity and related metabolic disorders.

Novel pyrrolocycloalkylpyrazole analogues as CB1 ligands

Novel 1,4-dihydropyrazolo[3,4-a]pyrrolizine-, 4,5-dihydro-1H-pyrazolo[4,3-g]indolizine- and 1,4,5,6-tetrahydropyrazolo[3,4-c]pyrrolo[1,2-a]azepine-3-carboxamide-based compounds were designed and synthesized for cannabinoid CB₁ and CB₂ receptor interactions. Any of the new synthesized compounds showed high affinity for CB₂ receptor with K_i values superior to 314 nm, whereas some of them showed moderate affinity for CB₁ receptor with K_i values inferior to 400 nm. 7-Chloro-1-(2,4-dichlorophenyl)-N-(homopiperidin-1-yl)-4,5-dihydro-1H-pyrazolo[4,3-g]indolizine-3-carboxamide (2j) exhibited good affinity for CB₁ receptor (K_i CB₁  = 81 nm) and the highest CB₂ /CB₁ selectively ratio (>12). Docking studies carried out on such compounds were performed using the hCB₁ X-ray in complex with the close pyrazole analogue AM6538 and disclosed specific pattern of interactions related to the tricyclic pyrrolopyrazole scaffolds as CB₁ ligands.

Pharmacological comparison of traditional and non-traditional cannabinoid receptor 1 blockers in rodent models in vivo

Cannabinoid receptor 1 (CB1R) antagonists have been proven to be effective anti-obesity drugs; however, psychiatric side effects have halted their pharmaceutical development worldwide. Despite the emergence of next generation CB1R blockers, a preclinical head to head comparison of the anti-obesity and psychiatric side effect profiles of the key compounds has not been performed. Here, we compared classical CB1R antagonists (rimonabant, taranabant, otenabant, ibipinabant, and surinabant) and non-traditional CB1R blockers (the partial agonist O-1269, the neutral antagonists VCHSR and LH-21 and the peripherally acting inverse agonist JD-5037) using an in vivo screening cascade. First, the potencies of these compounds to reduce CB1R agonist-induced hypothermia and decrease fasting-induced food intake were determined. Then, equipotent doses of the non-toxic compounds were compared in a diet-induced obesity (DIO) test, which includes measurements of metabolic syndrome markers. Psychiatric side effects were assessed by measuring anxiogenicity in an ultrasonic vocalization test. All classical CB1R blockers were centrally acting appetite suppressants and decreased body weight and food intake in an obesity-dependent manner, with only slight effects on metabolic syndrome markers. In addition, all classical CB1R blockers increased ultrasonic vocalization. Surprisingly, none of the non-classical CB1R blockers was eligible for the DIO comparison and side effect profiling. O-1269 and LH-21 induced convulsive behavior, whereas VCHSR and JD-5037 were devoid of any in vivo activity. The classical CB1R blockers displayed similar therapeutic and side effect profiles in vivo, whereas the available non-traditional CB1R blockers were not appropriate tools for testing the therapeutic potential of alternative CB1R inhibitors.

Tetrahydroindazole derivatives as potent and peripherally selective cannabinoid-1 (CB1) receptor inverse agonists

A series of potent and receptor-selective cannabinoid-1 (CB1) receptor inverse agonists has been discovered. Peripheral selectivity of the compounds was assessed by a mouse tissue distribution study, in which the concentrations of a test compound in both plasma and brain were measured. A number of peripherally selective compounds have been identified through this process. Compound 2p was further evaluated in a 3-week efficacy study in the diet-induced obesity (DIO) mouse model. Beneficial effects on plasma glucose were observed from the compound-treated mice.

Hypolipidemic effect of dihydroisoquinoline oxaziridine in high-fat diet-fed rats

Obesity is a serious health problem that increases the risk of many complications, including diabetes and cardiovascular disease. This study aims to evaluate, for the first time, the effects of oxaziridine 3 on lipoprotein lipase activity in the serum of rats fed with a high-fat diet (HFD) on body weight, lipid profile and liver-kidney functions. The administration of oxaziridine 3 to HFD-rats lowered body weight and inhibited the lipase activity of obese rats leading to notable decrease of T-Ch, TGs and LDL-Ch levels accompanied with an increase in HDL-Ch concentration in serum. Moreover, the findings of this study revealed that oxaziridine 3 helped to protect liver tissue from the appearance of fatty cysts. Additionally, oxaziridine 3 administration to HFD-rats induces antioxidant activity proven by the increase of superoxide dismutase (SOD) and catalase (CAT) activities and the decrease in Thiobarbituric acid reactive substances (TBARS) levels. It also induces the protection of liver-kidney functions confirmed by a decrease in the levels of toxicity parameters in blood.

A critical review of both the synthesis approach and the receptor profile of the 8-chloro-1-(2',4'-dichlorophenyl)-N-piperidin-1-yl-1,4,5,6-tetrahydrobenzo[6,7]cyclohepta[1,2-c]pyrazole-3-carboxamide and analogue derivatives

8-Chloro-1-(2',4'-dichlorophenyl)-N-piperidin-1-yl-1,4,5,6-tetrahydrobenzo[6,7]cyclohepta[1,2-c]pyrazole-3-carboxamide 9a was discovered as potent and selective CB1 antagonist by part of our group few years ago. In particular it was reported to have an affinity towards the CB1 cannabinoid receptor (CB1R), expressed as Ki, of 0.00035 nM. Nevertheless significantly divergent data were reported for the same compound from other laboratories. To unequivocally define the receptor profile of 9a, we have critically reviewed both its synthesis approach and binding data. Here we report that, in contrast to our previously reported data, 9a showed a Ki value for CB1R in the order of nanomolar rather than of fentomolar range. The new determined receptor profile of 9a was also ascertained for analogue derivatives 9b-i, as well as for 12. Moreover, the structural features of the synthesized compounds necessary for CB1R were investigated. Amongst the novel series, effects on CB1R intrinsic activity was highlighted due to the substituents at the position 3 of the pyrazole ring of the 1,4,5,6-tetrahydrobenzo[6,7]cyclohepta[1,2-c]pyrazole scaffold. Although the cannabinoid receptor profile of 9a was reviewed in this work, the relevance of this compound in CB1R antagonist based drug discovery is confirmed.

Endocannabinoids--at the crossroads between the gut microbiota and host metabolism

Various metabolic disorders are associated with changes in inflammatory tone. Among the latest advances in the metabolism field, the discovery that gut microorganisms have a major role in host metabolism has revealed the possibility of a plethora of associations between gut bacteria and numerous diseases. However, to date, few mechanisms have been clearly established. Accumulating evidence indicates that the endocannabinoid system and related bioactive lipids strongly contribute to several physiological processes and are a characteristic of obesity, type 2 diabetes mellitus and inflammation. In this Review, we briefly define the gut microbiota as well as the endocannabinoid system and associated bioactive lipids. We discuss existing literature regarding interactions between gut microorganisms and the endocannabinoid system, focusing specifically on the triad of adipose tissue, gut bacteria and the endocannabinoid system in the context of obesity and the development of fat mass. We highlight gut-barrier function by discussing the role of specific factors considered to be putative 'gate keepers' or 'gate openers', and their role in the gut microbiota-endocannabinoid system axis. Finally, we briefly discuss data related to the different pharmacological strategies currently used to target the endocannabinoid system, in the context of cardiometabolic disorders and intestinal inflammation.

Tricyclic pyrazoles. Part 8. Synthesis, biological evaluation and modelling of tricyclic pyrazole carboxamides as potential CB2 receptor ligands with antagonist/inverse agonist properties

Previous studies have investigated the relevance and structure-activity relationships (SARs) of pyrazole derivatives in relation with cannabinoid receptors, and the series of tricyclic 1,4-dihydroindeno[1,2-c]pyrazoles emerged as potent CB2 receptor ligands. In the present study, novel 1,4-dihydroindeno[1,2-c]pyrazole and 1H-benzo[g]indazole carboxamides containing a cyclopropyl or a cyclohexyl substituent were designed and synthesized to evaluate the influence of these structural modifications towards CB1 and CB2 receptor affinities. Among these derivatives, compound 15 (6-cyclopropyl-1-(2,4-dichlorophenyl)-N-(adamantan-1-yl)-1,4-dihydroindeno[1,2-c]pyrazole-3-carboxamide) showed the highest CB2 receptor affinity (Ki = 4 nM) and remarkable selectivity (KiCB1/KiCB2 = 2232), whereas a similar affinity, within the nM range, was seen for the fenchyl derivative (compound 10: Ki = 6 nM), for the bornyl analogue (compound 14: Ki = 38 nM) and, to a lesser extent, for the aminopiperidine derivative (compound 6: Ki = 69 nM). Compounds 10 and 14 were also highly selective for the CB2 receptor (KiCB1/KiCB2 > 1000), whereas compound 6 was relatively selective (KiCB1/KiCB2 = 27). The four compounds were also subjected to GTPγS binding analysis showing antagonist/inverse agonist properties (IC50 for compound 14 = 27 nM, for 15 = 51 nM, for 10 = 80 nM and for 6 = 294 nM), and this activity was confirmed for the three more active compounds in a CB2 receptor-specific in vitro bioassay consisting in the quantification of prostaglandin E2 release by LPS-stimulated BV2 cells, in the presence and absence of WIN55,212-2 and/or the investigated compounds. Modelling studies were also conducted with the four compounds, which conformed with the structural requirements stated for the binding of antagonist compounds to the human CB2 receptor.

Identifying the structural features and diversifying the chemical domain of peripherally acting CB1 receptor antagonists using molecular modeling techniques

A four featured pharmacophore and predictive 3D-QSAR models were developed which were used for virtual screening of the Asinex database to get chemically diverse hits of peripherally active CB1 receptor antagonists.

Mitochondrial ADP/ATP exchange inhibition: a novel off-target mechanism underlying ibipinabant-induced myotoxicity

Cannabinoid receptor 1 (CB1R) antagonists appear to be promising drugs for the treatment of obesity, however, serious side effects have hampered their clinical application. Rimonabant, the first in class CB1R antagonist, was withdrawn from the market because of psychiatric side effects. This has led to the search for more peripherally restricted CB1R antagonists, one of which is ibipinabant. However, this 3,4-diarylpyrazoline derivative showed muscle toxicity in a pre-clinical dog study with mitochondrial dysfunction. Here, we studied the molecular mechanism by which ibipinabant induces mitochondrial toxicity. We observed a strong cytotoxic potency of ibipinabant in C2C12 myoblasts. Functional characterization of mitochondria revealed increased cellular reactive oxygen species generation and a decreased ATP production capacity, without effects on the catalytic activities of mitochondrial enzyme complexes I-V or the complex specific-driven oxygen consumption. Using in silico off-target prediction modelling, combined with in vitro validation in isolated mitochondria and mitoplasts, we identified adenine nucleotide translocase (ANT)-dependent mitochondrial ADP/ATP exchange as a novel molecular mechanism underlying ibipinabant-induced toxicity. Minor structural modification of ibipinabant could abolish ANT inhibition leading to a decreased cytotoxic potency, as observed with the ibipinabant derivative CB23. Our results will be instrumental in the development of new types of safer CB1R antagonists.

New perspectives on the development of antiobesity drugs

After many years of research, obesity is still a disease with an unmet medical need. Very few compounds have been approved, acting mainly on neuromediators; researches, in recent years, pointed toward compounds potentially safer than first-generation antiobesity drugs, able to interact with one or more (multitarget therapy) receptors for substances produced by the gut, adipose tissue and other targets outside CNS. Other holistic approaches, such as those involving gut microbiota and plant extracts, appeared recently in the literature, and undoubtedly will contribute to the discovery of a valuable therapy for this disease. This review deals with the positive results and the pitfalls obtained following these approaches, with a view on their clinical trial studies.