Selective cannabinoid receptor 2 modulators: a patent review 2009--present

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 dysbiotic 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.

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.

Comprehensive comparison of different parts of Paeonia ostii, a food-medicine plant, based on untargeted metabolomics, quantitative analysis, and bioactivity analysis

Introduction

Paeonia ostii T. Hong & J.X. Zhang (s.s.) (Chinese name, Fengdan) is a widely cultivated food-medicine plant in China, in which root bark, seed kernels, and flowers are utilized for their medicinal and edible values. However, other parts of the plant are not used efficiently, in part due to a poor understanding of their chemical composition and potential biological activity.

Methods

Untargeted ultra-performance liquid chromatography-quadrupole time of flight-mass spectrometry (UPLC-Q-TOF-MS) metabolomics was applied to characterize the metabolic profiles of 10 different parts of P. ostii.

Results and discussion

A total of 160 metabolites were alternatively identified definitely or tentatively, which were significantly different in various plant parts by multivariate statistical analysis. Quantitative analysis showed that underutilized plant parts also contain many active ingredients. Compared with the medicinal part of root bark, the root core part still contains a higher content of paeoniflorin (17.60 ± 0.06 mg/g) and PGG (15.50 ± 2.00 mg/g). Petals, as an edible part, contain high levels of quercitrin, and stamens have higher methyl gallate and PGG. Unexpectedly, the ovary has the highest content of methyl gallate and rather high levels of PGG (38.14 ± 1.27 mg/g), and it also contains surprisingly high concentrations of floralalbiflorin I. Paeoniflorin (38.68 ± 0.76 mg/g) is the most abundant in leaves, and the content is even higher than in the root bark. Branches are also rich in a variety of catechin derivatives and active ingredients such as hydrolyzable tannins. Seed kernels also contain fairly high levels of paeoniflorin and albiflorin. Fruit shells still contain a variety of components, although not at high levels. Seed coats, as by-products removed from peony seeds before oil extraction, have high contents of stilbenes, such as trans-gnetin H and suffruticosol B, showing significant potential for exploitation. Except for the seed kernels, extracts obtained from other parts exhibited good antioxidant activity in DPPH, ABTS, and ferric ion reducing antioxidant power (FRAP) assays (0.09-1.52 mmol TE/g). Five compounds (gallic acid, PGG, trans-resveratrol, kaempferol, and quercitrin) were important ingredients that contributed to their antioxidant activities. Furthermore, P. ostii seed cakes were first reported to possess agonistic activity toward CB1/CB2 receptors. This study provides a scientific basis for the further development and utilization of P. ostii plant resources.

In vitro and in vivo pharmacology of nine novel synthetic cannabinoid receptor agonists

Synthetic cannabinoid receptor agonists (SCRAs) are novel psychoactive substances that bind to and activate CB1 receptors in the brain. The structural manipulations observed in newer SCRAs suggest that manufacturers have incorporated modern drug development techniques into their repertoire, often producing higher CB1 receptor affinity than Δ9-tetrahydrocannabinol (Δ9-THC). This study examined nine SCRAs recently detected by forensic surveillance, some of which caused fatalities: 5F-MDMB-PICA, FUB-144, 5F-MMB-PICA, MMB-4en-PICA, MMB-FUBICA, 5F-EDMB-PINACA, APP-BINACA, MDMB-4en-PINACA, and FUB-AKB48. Compounds were evaluated for CB1 and CB2 receptor binding affinity and functional activation and for their effects on body temperature, time course, and pharmacological equivalence with Δ9-THC in Δ9-THC drug discrimination in mice. All SCRAs bound to and activated CB1 and CB2 receptors with high affinity, with similar or greater affinity for CB2 than CB1 receptors and stimulated [35S]GTPγS binding in CB1 and CB2 expressing cell membranes. All compounds produced hypothermia, with shorter latency to peak effects for SCRAs than Δ9-THC. All SCRAs fully substituted for Δ9-THC in drug discrimination at one or more doses. Rank order potency in producing in vivo effects mostly aligned with rank order CB1 receptor affinities. Potencies for Δ9-THC-like discriminative stimulus effects were similar across sex except Δ9-THC was more potent in females and 5F-MMB-PICA was more potent in males. In summary, 5F-EMDB-PINACA, 5F-MDMB-PICA, MDMB-4en-PINACA, FUB-144, FUB-AKB48, 5F-MMB-PICA, MMB-4en-PICA, and MMB-FUBICA are potent and efficacious SCRAs with pharmacology like that of past SCRAs that have been abused in humans. In contrast, APP-BINACA was efficacious, but had lower potency than most past SCRAs.

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®.

VF-13, a chimeric peptide of VD-hemopressin(α) and neuropeptide VF, produces potent antinociception with reduced cannabinoid-related side effects

Pharmacological evidence indicated a functional interaction between neuropeptide FF (NPFF) and cannabinoid systems, and the cannabinoids combined with the NPFF receptor agonist neuropeptide VF (NPVF) produced antinociception without tolerance. In the present study, VF-13, a chimeric peptide containing the pharmacophores of the endogenous cannabinoid peptide VD-hemopressin(α) (VD-Hpα) and NPVF, was synthesized and pharmacologically evaluated. In vitro, VF-13 significantly upregulated the phosphorylated level of extracellular signal-regulated kinase 1/2 (ERK1/2) in CHO cells stably expressing CB1 receptors and inhibited forskolin-induced cAMP accumulation in HEK293 cells stably expressing NPFF₁ or NPFF₂ receptors. Moreover, VF-13 induced neurite outgrowth in Neuro 2A cells via CB1 and NPFF receptors. These results suggest that VF-13 exhibits multifunctional agonism at CB1, NPFF₁ and NPFF₂ receptors in vitro. Interestingly, intracerebroventricular VF-13 produced dose-dependent antinociception in mouse models of tail-flick and carrageenan-induced inflammatory pain via the TRPV1 receptor. In contrast, the reference compound (m)VD-Hpα-NH₂ induced CB1 receptor-mediated supraspinal antinociception. Additionally, subcutaneous injection of (m)VD-Hpα-NH₂ and VF-13 produced significant antinociception in carrageenan-induced inflammatory pain model. In the tetrad assay, our data demonstrated that VF-13 elicited hypothermia, but not catalepsy and hypoactivity after intracerebroventricular injection. Notably, VF-13 produced non-tolerance forming antinociception over 6 days treatment in both acute and inflammatory pain models. Furthermore, VF-13 had no apparent effects on gastrointestinal transit, pentobarbitone-induced sedation, food intake, and motor coordination at the supraspinal level. In summary, VF-13, a novel chimeric peptide of VD-Hpα and NPVF, produced non-tolerance forming antinociception in preclinical pain models with reduced cannabinoid-related side effects.

Development of Quinazoline/Pyrimidine-2,4(1H,3H)-diones as Agonists of Cannabinoid Receptor Type 2

Starting from a prototypical structure 1, we describe our efforts to design and obtain novel quinazoline/pyrimidine-2,4(1H,3H)-diones with high CB2 agonist potency and selectivity as well as improved physicochemical characteristics, mainly hydrophilicity. The most potent and selective CB2 agonists, 8 and 36, in this series were also endowed with lower logP values than that of GW842166X and lead compound 1. These derivatives appear to be promising lead compounds for the development of future CB2 agonists.

Cannabinoid receptor 2 (CB2) agonists and antagonists: a patent update

INTRODUCTION

Modulation of the CB2 receptor is an interesting approach for pain and inflammation, arthritis, addictions, neuroprotection, and cancer, among other possible therapeutic applications, and is devoid of central side effects.

AREAS COVERED

This review highlights the novel scaffolds for CB2 ligands and the diverse therapeutic applications for CB2 modulators disclosed in patents published since 2012.

EXPERT OPINION

Structural diversity of CB2 modulator scaffolds characterized the patent literature. Several CB2 agonists reached clinical Phase II for pain management and inflammation. Other therapeutic applications need to be explored such as neuroprotection and/or neurodegeneration.

Emerging targets in treating pain

PURPOSE OF REVIEW

To provide an overview on drug targets and emerging pharmacological treatment options for chronic pain.

RECENT FINDINGS

Chronic pain poses an enormous socioeconomic burden for the more than 30% of people who suffer from it, costing over $600 billion per year in the USA. In recent years, there has been a surge in preclinical and clinical research endeavors to try to stem this epidemic. Preclinical studies have identified a wide array of potential targets, with some of the most promising translational research being performed on novel opioid receptors, cannabinoid receptors, selective ion channel blockers, cytokine inhibitors, nerve growth factor inhibitors, N-methyl-D-aspartate receptor antagonists, glial cell inhibitors, and bisphosphonates.

SUMMARY

There are many obstacles for the development of effective medications to treat chronic pain, including the inherent challenges in identifying pathophysiological mechanisms, the overlap and multiplicity of pain pathways, and off-target adverse effects stemming from the ubiquity of drug target receptor sites and the lack of highly selective receptor ligands. Despite these barriers, the number and diversity of potential therapies have continued to grow, to include disease-modifying and individualized drug treatments.

Development of Quinoline-2,4(1H,3H)-diones as Potent and Selective Ligands of the Cannabinoid Type 2 Receptor

The cannabinoid type 2 receptors (CB2Rs) play crucial roles in inflammatory diseases. There has been considerable interest in developing potent and selective ligands for CB2R. In this study, quinoline-2,4(1H,3H)-dione analogs have been designed, synthesized, and evaluated for their potencies and binding properties toward the cannabinoid type 1 receptor (CB1R) and CB2R. C5- or C8-substituted quinoline-2,4(1H,3H)-diones demonstrate CB2R agonist activity, while the C6- or C7-substituted analogs are antagonists of CB2R. In addition, oral administration of 21 dose-dependently alleviates the clinical symptoms of experimental autoimmune encephalomyelitis in a mouse model of multiple sclerosis and protects the central nervous system from immune damage. Furthermore, the interaction modes predicted by docking simulations and the 3D-QSAR model generated with CoMFA may offer guidance for further design and modification of CB2R modulators.

Towards a personalized treatment in depression: endocannabinoids, inflammation and stress response

The complex nature of depression is mirrored by difficulties in tailoring its treatment. Key underlying mechanisms of this mental disorder include elevated inflammation and a dysregulated hypothalamic-pituitary-adrenal (HPA) axis. More recently, the endocannabinoid system has been proposed as another important component in the pathogenesis of depression, and strong evidence suggests that all three systems communicate with each other. A growing number of genetic studies have investigated polymorphisms in depression in each of these systems separately. However, no study to date has looked at these genes in conjunction. In this article we will review the crosstalk between the endocannabinoid system, immune system and HPA axis; and discuss the evidence of gene polymorphisms and their relation to the risk of depression and its treatment. We propose future directions where genes of these three systems are considered from a joint perspective to improve prediction of treatment response, taking into account potentially overlooked genetic variations.

Selective CB2 receptor agonists. Part 1: the identification of novel ligands through computer-aided drug design (CADD) approaches

Computer-aided drug design scaffold hopping strategies were utilized to identify new classes of CB2 agonists when compounds of an established series with low nanomolar potency were challenging to optimize for good drug-like properties. Use of ligand-based design strategies through BI Builder (a tool for de novo design) and PharmShape (a virtual screening software package) approaches led to the discovery of new chemotypes. Specifically, compounds containing azetidine-, proline-, and piperidine-based cores were found to have low nanomolar and picomolar CB2 agonist activities with drug-like properties considered appropriate for early profiling.

Differential activation of intracellular versus plasmalemmal CB2 cannabinoid receptors

The therapeutic and psychoactive properties of cannabinoids have long been recognized. The type 2 receptor for cannabinoids (CB₂) has emerged as an important therapeutic target in several pathologies, as it mediates beneficial effects of cannabinoids while having little if any psychotropic activity. Difficulties associated with the development of CB₂-based therapeutic agents have been related to its intricate pharmacology, including the species specificity and functional selectivity of the CB₂-initiated responses. We postulated that a plasmalemmal or subcellular location of the receptor may contribute to the differential signaling pathways initiated by its activation. To differentiate between these two, we used extracellular and intracellular administration of CB₂ ligands and concurrent calcium imaging in CB₂-expressing U2OS cells. We found that extracellular administration of anandamide was ineffective, whereas 2-arachidonoyl glycerol (2-AG) and WIN55,212-2 triggered delayed, CB₂-dependent Ca²⁺ responses that were Gq protein-mediated. When microinjected, all agonists elicited fast, transient, and dose-dependent elevations in intracellular Ca²⁺ concentration upon activation of Gq-coupled CB₂ receptors. The CB₂ dependency was confirmed by the sensitivity to AM630, a selective CB₂ antagonist, and by the unresponsiveness of untransfected U2OS cells to 2-AG, anandamide, or WIN55,212-2. Moreover, we provide functional and morphological evidence that CB₂ receptors are localized at the endolysosomes, while their activation releases Ca²⁺ from inositol 1,4,5-trisphosphate-sensitive- and acidic-like Ca²⁺ stores. Our results support the functionality of intracellular CB₂ receptors and their ability to couple to Gq and elicit Ca²⁺ signaling. These findings add further complexity to CB₂ receptor pharmacology and argue for careful consideration of receptor localization in the development of CB₂-based therapeutic agents.

Cannabinoids in pain management: CB1, CB2 and non-classic receptor ligands

INTRODUCTION

Commercially available cannabinoids are subject to psychotomimetic and addiction (cannabinomimetic) adverse effects largely through activation of the cannabinoid 1 receptor (CB1r). The available commercial cannabinoids have a narrow therapeutic index. Recently developed peripherally restricted cannabinoids, regionally administered cannabinoids, bifunctional cannabinoid ligands and cannabinoid enzyme inhibitors, endocannabinoids, which do not interact with classic cannabinoid receptors (CB1r and CB2r), cannabinoid receptor antagonists and selective CB1r agonists hold promise as analgesics.

AREAS COVERED

This author provides a review of the current investigational cannabinoids currently in development for pain management. The author also provides their perspective on the future of the field.

EXPERT OPINION

Regional and peripherally restricted cannabinoids will reduce cannabinomimetic side effects. Spinal cannabinoids may increase the therapeutic index by limiting the dose necessary for response and minimize drugs exposure to supraspinal sites where cannabinomimetic side effects originate. Cannabinoid bifunctional ligands should be further explored. The combination of a CB2r agonist with a transient receptor potential vanilloid (TRPV-1) antagonist may improve the therapeutic index of the CB2r agonist. Enzyme inhibitors plus TRPV-1 blockers should be further explored. The development of analgesic tolerance with enzyme inhibitors and the pronociceptive effects of prostamides limit the benefits to cannabinoid hydrolyzing enzyme inhibitors. Most clinically productive development of cannabinoids over the next 5 years will be in the area of selective CB2r agonists. These agents will be tested in various inflammatory, osteoarthritis and neuropathic pains.

CB2 cannabinoid receptor is a novel target for third-generation selective estrogen receptor modulators bazedoxifene and lasofoxifene

The purpose of the current study was to investigate the ability of the third-generation selective estrogen receptor modulators (SERMs) bazedoxifene and lasofoxifene to bind and act on CB2 cannabinoid receptor. We have identified, for the first time, that CB2 is a novel target for bazedoxifene and lasofoxifene. Our results showed that bazedoxifene and lasofoxifene were able to compete for specific [(3)H]CP-55,940 binding to CB2 in a concentration-dependent manner. Our data also demonstrated that by acting on CB2, bazedoxifene and lasofoxifene concentration-dependently enhanced forskolin-stimulated cAMP accumulation. Furthermore, bazedoxifene and lasofoxifene caused parallel, rightward shifts of the CP-55,940, HU-210, and WIN55,212-2 concentration-response curves without altering the efficacy of these cannabinoid agonists on CB2, which indicates that bazedoxifene- and lasofoxifene-induced CB2 antagonism is most likely competitive in nature. Our discovery that CB2 is a novel target for bazedoxifene and lasofoxifene suggests that these third-generation SERMs can potentially be repurposed for novel therapeutic indications for which CB2 is a target. In addition, identifying bazedoxifene and lasofoxifene as CB2 inverse agonists also provides important novel mechanisms of actions to explain the known therapeutic effects of these SERMs.

Selective cannabinoid receptor type 2 (CB2) agonists: optimization of a series of purines leading to the identification of a clinical candidate for the treatment of osteoarthritic pain

A focused screening strategy identified thienopyrimidine 12 as a cannabinoid receptor type 2 agonist (hCB2) with moderate selectivity over the hCB1 receptor. This initial hit suffered from poor in vitro metabolic stability and high in vivo clearance. Structure-activity relationships describe the optimization and modification to a new more polar series of purine CB2 agonists. Examples from this novel scaffold were found to be highly potent and fully efficacious agonists of the human CB2 receptor with excellent selectivity against CB1, often having no CB1 agonist activity at the highest concentration measured (>100 μM). Compound 26 is a centrally penetrant molecule which possesses good biopharmaceutical properties, is highly water-soluble, and demonstrates robust oral activity in rodent models of joint pain. In addition, the peripherally restricted molecule 22 also demonstrated significant efficacy in the same analgesic model of rodent inflammatory pain.

Identification of raloxifene as a novel CB2 inverse agonist

The purpose of the current study was to apply a high throughput assay to systematically screen a library of food and drug administration (FDA)-approved drugs as potential ligands for the cannabinoid receptor 2 (CB2). A cell-based, homogenous time resolved fluorescence (HTRF) method for measuring changes in intracellular cAMP levels was validated and found to be suitable for testing ligands that may act on CB2. Among the 640 FDA-approved drugs screened, raloxifene, a drug used to treat/prevent post-menopausal osteoporosis, was identified for the first time to be a novel CB2 inverse agonist. Our results demonstrated that by acting on CB2, raloxifene enhances forskolin-stimulated cAMP accumulation in a concentration-dependant manner. Furthermore, our data showed that raloxifene competes concentration-dependently for specific [(3)H]CP-55,940 binding to CB2. In addition, raloxifene pretreatment caused a rightward shift of the concentration-response curves of the cannabinoid agonists CP-55,940, HU-210, and WIN55,212-2. Raloxifene antagonism is most likely competitive in nature, as these rightward shifts were parallel and were not associated with any changes in the efficacy of cannabinoid agonists on CB2. Our discovery that raloxfiene is an inverse agonist for CB2 suggests that it might be possible to repurpose this FDA-approved drug for novel therapeutic indications for which CB2 is a target. Furthermore, identifying raloxifene as a CB2 inverse agonist also provides important novel mechanisms of actions to explain the known therapeutic effects of raloxifene.