Selective Cannabinoid 2 Receptor Agonists as Potential Therapeutic Drugs for the Treatment of Endotoxin-Induced Uveitis

A systematic review of novel cannabinoids and their targets: Insights into the significance of structure in activity

To provide a comprehensive framework of the current information on the potency and efficacy of interaction between phyto- and synthetic cannabinoids and their respective receptors, an electronic search of the PubMed, Scopus, and EMBASE literature was performed. Experimental studies included reports of mechanistic data providing affinity, efficacy, and half-maximal effective concentration (EC50). Among the 108 included studies, 174 structures, and 16 targets were extracted. The most frequent ligands belonged to the miscellaneous category with 40.2% followed by phytocannabinoid-similar, indole-similar, and pyrrole-similar structures with an abundance of 17.8%, 16.6%, and 12% respectively. 64.8% of structures acted as agonists, 17.1 % appeared as inverse agonists, 10.8% as antagonists, and 7.2% of structures were reported with antagonist/inverse agonist properties. Our outcomes identify the affinity, EC50, and efficacy of the interactions between cannabinoids and their corresponding receptors and the subsequent response, evaluated in the available evidence. Considering structures' significance and very important effects of on the activities, the obtained results also provide clues to drug repurposing.

Cannabinoid CB2 receptor orthologues; in vitro function and perspectives for preclinical to clinical translation

Cannabinoid CB2 receptor agonists are in development as therapeutic agents, including for immune modulation and pain relief. Despite promising results in rodent preclinical studies, efficacy in human clinical trials has been marginal to date. Fundamental differences in ligand engagement and signalling responses between the human CB2 receptor and preclinical model species orthologues may contribute to mismatches in functional outcomes. This is a tangible possibility for the CB2 receptor in that there is a relatively large degree of primary amino acid sequence divergence between human and rodent. Here, we summarise CB2 receptor gene and protein structure, assess comparative molecular pharmacology between CB2 receptor orthologues, and review the current status of preclinical to clinical translation for drugs targeted at the CB2 receptor, focusing on comparisons between human, mouse and rat receptors. We hope that raising wider awareness of, and proposing strategies to address, this additional challenge in drug development will assist in ongoing efforts toward successful therapeutic translation of drugs targeted at the CB2 receptor. LINKED ARTICLES: This article is part of a themed issue Therapeutic Targeting of G Protein-Coupled Receptors: hot topics from the Australasian Society of Clinical and Experimental Pharmacologists and Toxicologists 2021 Virtual Annual Scientific Meeting. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.14/issuetoc.

Patent review of cannabinoid receptor type 2 (CB2R) modulators (2016-present)

INTRODUCTION

Cannabinoid receptor type 2 (CB2R), predominantly expressed in immune tissues, is believed to play a crucial role within the body's protective mechanisms. Its modulation holds immense therapeutic promise for addressing a wide spectrum of disbiotic conditions, including cardiovascular, gastrointestinal, liver, kidney, neurodegenerative, psychiatric, bone, skin, and autoimmune diseases, as well as lung disorders, cancer, and pain management.

AREAS COVERED

This review is an account of patents from 2016 up to 2023 which describes novel CB2R ligands, therapeutic applications, synthesis as well as formulations of CB2R modulators.

EXPERT OPINION

The patents cover a vast, structurally diverse chemical space. The focus of CB2R ligand development has shifted from unselective dual cannabinoid receptor type 1 (CB1R) and 2 agonists toward agonists with high selectivity over CB1R, particularly for indications associated with inflammation and tissue injury. Currently, there are at least eight CB2R agonists and one antagonist in active clinical development. A better understanding of the endocannabinoid system (ECS) and in particular of CB2R pharmacology is required to unlock the receptor's full therapeutic potential.

Enantiomeric Agonists of the Type 2 Cannabinoid Receptor Reduce Retinal Damage during Proliferative Vitreoretinopathy and Inhibit Hyperactive Microglia In Vitro

Microglia are resident immune cells of the central nervous system (CNS) and propagate inflammation following damage to the CNS, including the retina. Proliferative vitreoretinopathy (PVR) is a condition that can emerge following retinal detachment and is characterized by severe inflammation and microglial proliferation. The type 2 cannabinoid receptor (CB2) is an emerging pharmacological target to suppress microglial-mediated inflammation when the eyes or brain are damaged. CB2-knockout mice have exacerbated inflammation and retinal pathology during experimental PVR. We aimed to assess the anti-inflammatory effects of CB2 stimulation in the context of retinal damage and also explore the mechanistic roles of CB2 in microglia function. To target CB2, we used a highly selective agonist, HU-308, as well as its enantiomer, HU-433, which is a putative selective agonist. First, β-arrestin2 and Gαi recruitment was measured to compare activation of human CB2 in an in vitro heterologous expression system. Both agonists were then utilized in a mouse model of PVR, and the effects on retinal damage, inflammation, and cell death were assessed. Finally, we used an in vitro model of microglia to determine the effects of HU-308 and HU-433 on phagocytosis, cytokine release, migration, and intracellular signaling. We observed that HU-308 more strongly recruited both β-arrestin2 and Gαi compared to HU-433. Stimulation of CB2 with either drug effectively blunted LPS- and IFNγ-mediated signaling as well as NO and TNF release from microglia. Furthermore, both drugs reduced IL-6 accumulation, total caspase-3 cleavage, and retinal pathology following the induction of PVR. Ultimately, this work supports that CB2 is a valuable target for drugs to suppress inflammation and cell death associated with infection or sterile retinopathy, although the magnitude of effector recruitment may not be predictive of anti-inflammatory capacity.

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.

Development of Potent and Selective Monoacylglycerol Lipase Inhibitors. SARs, Structural Analysis, and Biological Characterization

New potent, selective monoacylglycerol lipase (MAGL) inhibitors based on the azetidin-2-one scaffold ((±)-5a-v, (±)-6a-j, and (±)-7a-d) were developed as irreversible ligands, as demonstrated by enzymatic and crystallographic studies for (±)-5d, (±)-5l, and (±)-5r. X-ray analyses combined with extensive computational studies allowed us to clarify the binding mode of the compounds. 5v was identified as selective for MAGL when compared with other serine hydrolases. Solubility, in vitro metabolic stability, cytotoxicity, and absence of mutagenicity were determined for selected analogues. The most promising compounds ((±)-5c, (±)-5d, and (±)-5v) were used for in vivo studies in mice, showing a decrease in MAGL activity and increased 2-arachidonoyl-sn-glycerol levels in forebrain tissue. In particular, 5v is characterized by a high eudysmic ratio and (3R,4S)-5v is one of the most potent irreversible inhibitors of h/mMAGL identified thus far. These results suggest that the new MAGL inhibitors have therapeutic potential for different central and peripheral pathologies.

Goods and Bads of the Endocannabinoid System as a Therapeutic Target: Lessons Learned after 30 Years

The cannabis derivative marijuana is the most widely used recreational drug in the Western world and is consumed by an estimated 83 million individuals (∼3% of the world population). In recent years, there has been a marked transformation in society regarding the risk perception of cannabis, driven by its legalization and medical use in many states in the United States and worldwide. Compelling research evidence and the Food and Drug Administration cannabis-derived cannabidiol approval for severe childhood epilepsy have confirmed the large therapeutic potential of cannabidiol itself, Δ9-tetrahydrocannabinol and other plant-derived cannabinoids (phytocannabinoids). Of note, our body has a complex endocannabinoid system (ECS)-made of receptors, metabolic enzymes, and transporters-that is also regulated by phytocannabinoids. The first endocannabinoid to be discovered 30 years ago was anandamide (N-arachidonoyl-ethanolamine); since then, distinct elements of the ECS have been the target of drug design programs aimed at curing (or at least slowing down) a number of human diseases, both in the central nervous system and at the periphery. Here a critical review of our knowledge of the goods and bads of the ECS as a therapeutic target is presented to define the benefits of ECS-active phytocannabinoids and ECS-oriented synthetic drugs for human health. SIGNIFICANCE STATEMENT: The endocannabinoid system plays important roles virtually everywhere in our body and is either involved in mediating key processes of central and peripheral diseases or represents a therapeutic target for treatment. Therefore, understanding the structure, function, and pharmacology of the components of this complex system, and in particular of key receptors (like cannabinoid receptors 1 and 2) and metabolic enzymes (like fatty acid amide hydrolase and monoacylglycerol lipase), will advance our understanding of endocannabinoid signaling and activity at molecular, cellular, and system levels, providing new opportunities to treat patients.

CB2 receptor in the CNS: from immune and neuronal modulation to behavior

Despite low levels of cannabinoid receptor type 2 (CB2R) expression in the central nervous system in human and rodents, a growing body of evidence shows CB2R involvement in many processes at the behavioral level, through both immune and neuronal modulations. Recent in vitro and in vivo evidence have highlighted the complex role of CB2R under physiological and inflammatory conditions. Under neuroinflammatory states, its activation seems to protect the brain and its functions, making it a promising target in a wide range of neurological disorders. Here, we provide a complete and updated overview of CB2R function in the central nervous system of rodents, spanning from modulation of immune function in microglia but also in other cell types, to behavior and neuronal activity, in both physiological and neuroinflammatory contexts.

Cannabinoid-Based Ocular Therapies and Formulations

The interest in the pharmacological applications of cannabinoids is largely increasing in a wide range of medical areas. Recently, research on its potential role in eye conditions, many of which are chronic and/or disabling and in need of new alternative treatments, has intensified. However, due to cannabinoids’ unfavorable physicochemical properties and adverse systemic effects, along with ocular biological barriers to local drug administration, drug delivery systems are needed. Hence, this review focused on the following: (i) identifying eye disease conditions potentially subject to treatment with cannabinoids and their pharmacological role, with emphasis on glaucoma, uveitis, diabetic retinopathy, keratitis and the prevention of Pseudomonas aeruginosa infections; (ii) reviewing the physicochemical properties of formulations that must be controlled and/or optimized for successful ocular administration; (iii) analyzing works evaluating cannabinoid-based formulations for ocular administration, with emphasis on results and limitations; and (iv) identifying alternative cannabinoid-based formulations that could potentially be useful for ocular administration strategies. Finally, an overview of the current advances and limitations in the field, the technological challenges to overcome and the prospective further developments, is provided.

Is there a rational basis for cannabinoids research and development in ocular pain therapy? A systematic review of preclinical evidence

BACKGROUND

Purpose of the present systematic review is to investigate preclinical evidence in favor of the working hypothesis of efficacy of cannabinoids in ocular pain treatment.

METHODS

Literature search includes the most relevant repositories for medical scientific literature from inception until November, 24 2021. Data collection and selection of retrieved records adhere to PRISMA criteria.

RESULTS

In agreement with a priori established protocol the search retrieved 2471 records leaving 479 results after duplicates removal. Eleven records result from title and abstract screening to meet the inclusion criteria; only 4 results are eligible for inclusion in the qualitative synthesis impeding meta-analysis. The qualitative analysis highlights the antinociceptive and anti-inflammatory efficacy of Δ8-tetrahydrocannabinol, cannabidiol and its derivative HU-308 and of new racemic CB1 allosteric ligand GAT211 and its enantiomers GAT228 and GAT229. Moreover, CB2R agonists RO6871304 and RO6871085 and CB2R ligand HU910 provide evidence of anti-inflammatory efficacy. CB2 agonist HU308 reduces of 241% uveitis-induced leukocyte adhesion and changes lipidome profile. Methodological and design issues raise concern of risk of bias and the amount of studies is too small for generalization. Furthermore, the ocular pain model used can resemble only inflammatory but not neuropathic pain.

CONCLUSIONS

The role of the endocannabinoid system in ocular pain is underinvestigated, since only two studies assessing the effects of cannabinoid receptors modulators on pain behavior and other two on pain-related inflammatory processes are found. Preclinical studies investigating the efficacy of cannabinoids in ocular inflammatory and neuropathic pain models are needed to pave the way for clinical translation.

Real-Time Imaging of Immune Modulation by Cannabinoids Using Intravital Fluorescence Microscopy

Introduction: The endocannabinoid system (ECS) is an endogenous regulatory system involved in a wide range of physiologic and disease processes. Study of ECS regulation provides novel drug targets for disease treatment. Intravital microscopy (IVM), a microscopy-based imaging method that allows the observation of cells and cell-cell interactions within various tissues and organs in vivo, has been utilized to study tissues and cells in their physiologic microenvironment. This article reviews the current state of the IVM techniques used in ECS-related inflammation research. Methodological Aspects of IVM: IVM with focus on conventional fluorescent microscope has been introduced in investigation of microcirculatory function and the behavior of individual circulating cells in an in vivo environment. Experimental setting, tissue protection under physiologic condition, and microscopical observation are described. Application of IVM in Experimental Inflammatory Disorders: Using IVM to investigate the effects of immune modulation by cannabinoids is extensively reviewed. The inflammatory disorders include sepsis, arthritis, diabetes, interstitial cystitis, and inflammatory conditions in the central nervous system and eyes. Conclusion: IVM is a critical tool in cannabinoid and immunology research. It has been applied to investigate the role of the ECS in physiologic and disease processes. This review demonstrates that the IVM technique provides a unique means in understanding ECS regulation on immune responses in diseases under their physical conditions, which could not be achieved by other methods.

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®.

First In Class (S,E)-11-[2-(Arylmethylene)Hydrazono]-PBD Analogs As Selective CB2 Modulators Targeting Neurodegenerative Disorders

Newly designed pyrrolo[2,1-c][1,4]benzodiazepines tricyclic skeleton has shown potential clusters of cannabinoid receptors CB1/CB2 selective ligands. CB2 plays a critical role in microglial-derived neuroinflammation, where it modulates cell proliferation, migration, and differentiation into M1 or M2 phenotypes. Beginning with computer-based docking studies accounting the recently discovered X-ray crystal structure of CB2, we designed a series of PBD analogs as potential ligands of CB2 and tested their binding affinities. Interestingly, computational studies and theoretical binding affinities of several selected (S,E)-11-[2-(arylmethylene)hydrazono]-PBD analogs, have revealed the presence of potential selectivity in binding attraction towards CB1 and CB2. Reported here is the discovery of the first representatives of this series of selective binding to CB2. Preliminary data showed that this class of molecules display potential binding efficacy towards the cannabinoid receptors tested. Intriguingly, initial cannabinoid binding assay showed a selective binding affinity of 4g and 4h showed K _i of 0.49 and 4.7 μM towards CB2 receptors while no binding was observed to CB1. The designed leads have shown remarkable stability pattern at the physiological pH magnifying their therapeutic values. We hypothesize that the PBD tricyclic structure offers the molecule an appropriate three-dimensional conformation to fit snugly within the active site of CB2 receptors, giving them superiority over the reported CB2 agonists/inverse agonists. Our findings suggested that the attachment of heterocyclic ring through the condensation of diazepine hydrazone and S- or N-heterocyclic aldehydes enhances the selectivity of CB2 over CB1.