Rational Design, Synthesis, and Pharmacological Properties of New 1,8-Naphthyridin-2(1H)-on-3-Carboxamide Derivatives as Highly Selective Cannabinoid-2 Receptor Agonists

Synthesis, design, and antiproliferative evaluation of 6-(N-Substituted-methyl)pyrazolo[3,4-d]pyrimidines as the potent anti-leukemia agents

Pyrazolopyrimidine derivatives, including pyrazolopyrimidines, 6-aminopyrazolopyrimidines, 6-[(formyloxy)methyl]pyrazolopyrimidines, 6-(hydroxymethyl)pyrazolopyrimidine, and 6-(aminomethyl)pyrazolopyrimidines have been successfully prepared and tested against NCI-H226, NPC-TW01, and Jurkat cancer cell lines. Among the tested pyrazolopyrimidine compounds, we found 6-aminopyrazolopyrimidines and 6-(aminomethyl)pyrazolopyrimidines with essential o-ClPh or p-ClPh substituted moieties on N-1 pyrazole ring exhibited the best IC50 inhibition activity for Jurkat cells. Furthermore, optimization of the SAR study on the C-6 position of pyrazolopyrimidine ring demonstrated that 6-(N-substituted-methyl)pyrazolopyrimidines 17b, 17d, and 19d possessed the significant IC50 inhibitory activity for the different leukemia cell lines, especially for Jurkat, K-562, and HL-60. On the other hand, further SAR inhibition and docking model studies revealed that compound 19d, which has a 3-(1H-imidazol-1-yl)propan-1-amino side-chain on the C-6 position, was able to form four hydrogen bonds with residues Ala226, Leu152, and Glu194 and specifically extended into the P1 pocket subsite with Aurora A, resulting in improved inhibitory activity almost similar to SNS-314. To explore the anti-cancer mechanism, compound 19d was measured by Western blot analysis in Jurkat T-cells, however, it showed non-responsibility to Aurora B. For the further structural modifications on the lateral chain of compound 19d, compounds 24 with longer lateral chain were designed and synthesized for testing leukemia cell lines. However, compounds 24 was significantly decrease inhibition potency against leukemia cell lines. Based on the in-vitro results, compounds 17b and 19d could be considered to be the best potential lead drug in our study for the development of new and effective therapies for leukemia treatment. On the other hand, the DHFR inhibition results indicated compound 19d possessed good inhibitory activity and better than the reported naphthalene derivative. Through further comparisons of the model superposition of three-dimensional (3D) conformations in DHFR, compound 19d presented a similar structural alignment to Methotrexate and the reported naphthalene derivative and led to similar drug-like functional relationships. As a results, compound 19d would be a potential DHFR inhibitor for anti-leukemia drug candidate.

Synthesis, Structure-Activity Relationships, Radiofluorination, and Biological Evaluation of [18F]RM365, a Novel Radioligand for Imaging the Human Cannabinoid Receptor Type 2 (CB2R) in the Brain with PET

The development of cannabinoid receptor type 2 (CB2R) PET radioligands has been intensively explored due to the pronounced CB2R upregulation under various pathological conditions. Herein, we report on the synthesis of a series of CB2R affine fluorinated indole-2-carboxamide ligands. Compound RM365 was selected for PET radiotracer development due to its high CB2R affinity (Ki = 2.1 nM) and selectivity over CB1R (factor > 300). Preliminary in vitro evaluation of [18F]RM365 indicated species differences in the binding to CB2R (KD of 2.32 nM for the hCB2R vs KD > 10,000 nM for the rCB2R). Metabolism studies in mice revealed a high in vivo stability of [18F]RM365. PET imaging in a rat model of local hCB2R(D80N) overexpression in the brain demonstrates the ability of [18F]RM365 to reach and selectively label the hCB2R(D80N) with a high signal-to-background ratio. Thus, [18F]RM365 is a very promising PET radioligand for the imaging of upregulated hCB2R expression under pathological conditions.

Novel Cannabinoid Receptor 2 (CB2) Low Lipophilicity Agonists Produce Distinct cAMP and Arrestin Signalling Kinetics without Bias

Cannabinoid Receptor 2 (CB2) is a promising target for treating inflammatory diseases. We designed derivatives of 3-carbamoyl-2-pyridone and 1,8-naphthyridin-2(1H)-one-3-carboxamide CB2-selective agonists with reduced lipophilicity. The new compounds were measured for their affinity (radioligand binding) and ability to elicit cyclic adenosine monophosphate (cAMP) signalling and β-arrestin-2 translocation with temporal resolution (BRET-based biosensors). For the 3-carbamoyl-2-pyridone derivatives, we found that modifying the previously reported compound UOSS77 (also known as S-777469) by appending a PEG2-alcohol via a 3-carbomylcyclohexyl carboxamide (UOSS75) lowered lipophilicity, and preserved binding affinity and signalling profile. The 1,8-naphthyridin-2(1H)-one-3-carboxamide UOMM18, containing a cis configuration at the 3-carboxamide cyclohexyl and with an alcohol on the 4-position of the cyclohexyl, had lower lipophilicity but similar CB2 affinity and biological activity to previously reported compounds of this class. Relative to CP55,940, the new compounds acted as partial agonists and did not exhibit signalling bias. Interestingly, while all compounds shared similar temporal trajectories for maximal efficacy, differing temporal trajectories for potency were observed. Consequently, when applied at sub-maximal concentrations, CP55,940 tended to elicit sustained (cAMP) or increasing (arrestin) responses, whereas responses to the new compounds tended to be transient (cAMP) or sustained (arrestin). In future studies, the compounds characterised here may be useful in elucidating the consequences of differential temporal signalling profiles on CB2-mediated physiological responses.

Design, synthesis and biological evaluation of novel orthosteric-allosteric ligands of the cannabinoid receptor type 2 (CB2R)

It is well known that G protein–coupled receptors (GPCRs) assume multiple active states. Orthosteric ligands and/or allosteric modulators can preferentially stabilize specific conformations, giving rise to pathway-biased signaling. One of the most promising strategies to expand the repertoire of signaling-selective GPCR activators consists of dualsteric agents, which are hybrid compounds consisting of orthosteric and allosteric pharmacophoric units. This approach proved to be very promising showing several advantages over monovalent targeting strategies, including an increased affinity or selectivity, a bias in signaling pathway activation, reduced off-target activity and therapeutic resistance. Our study focused on the cannabinoid receptor type 2 (CB₂R), considered a clinically promising target for the control of brain damage in neurodegenerative disorders. Indeed, CB₂R was found highly expressed in microglial cells, astrocytes, and even in some neuron subpopulations. Here, we describe the design, synthesis, and biological evaluation of two new classes of potential dualsteric (bitopic) CB₂R ligands. The new compounds were obtained by connecting, through different linkers, the pharmacophoric portion of the CB₂R positive allosteric modulator (PAM), EC21a, with that of the CB₂R selective orthosteric agonist LV62, both developed in our laboratories. A preliminary screening enabled us to identify compound JR64a as the most promising of the series. Indeed, functional examination highlighted a signaling ‘bias’ in favor of G protein activation over βarrestin2 recruitment, combined with high affinity for CB₂R and the ability to efficiently prevent inflammation in human microglial cells (HMC3) exposed to LPS/TNFα stimulation, thus demonstrating great promise for the treatment of neurodegenerative diseases.

Structure-Based Design, Optimization, and Development of [18F]LU13: A Novel Radioligand for Cannabinoid Receptor Type 2 Imaging in the Brain with PET

The cannabinoid receptor type 2 (CB2R) is an attractive target for the diagnosis and therapy of neurodegenerative diseases and cancer. In this study, we aimed at the development of a novel ¹⁸F-labeled radioligand starting from the structure of the known naphthyrid-2-one CB2R ligands. Compound 28 (LU13) was identified with the highest binding affinity and selectivity versus CB1R (CB2RK_i = 0.6 nM; CB1RK_i/CB2RK_i > 1000) and was selected for radiolabeling with fluorine-18 and biological characterization. The new radioligand [¹⁸F]LU13 showed high CB2R affinity in vitro as well as high metabolic stability in vivo. PET imaging with [¹⁸F]LU13 in a rat model of vector-based/-related hCB2R overexpression in the striatum revealed a high signal-to-background ratio. Thus, [¹⁸F]LU13 is a novel and highly promising PET radioligand for the imaging of upregulated CB2R expression under pathological conditions in the brain.

Synthesis and In Vitro Characterization of Selective Cannabinoid CB2 Receptor Agonists: Biological Evaluation against Neuroblastoma Cancer Cells

1,8-naphthyridine-3-carboxamide structures were previously identified as a promising scaffold from which to obtain CB2R agonists with anticancer and anti-inflammatory activity. This work describes the synthesis and functional characterization of new 1,8-naphthyridin-2(1H)-one-3-carboxamides with high affinity and selectivity for CB2R. The new compounds were able to pharmacologically modulate the cAMP response without modulating CB2R-dependent β-arrestin2 recruitment. These structures were also evaluated for their anti-cancer activity against SH-SY5Y and SK-N-BE cells. They were able to reduce the cell viability of both neuroblastoma cancer cell lines with micromolar potency (IC50 of FG158a = 11.8 μM and FG160a = 13.2 μM in SH-SY5Y cells) by a CB2R-mediated mechanism. Finally, in SH-SY5Y cells one of the newly synthesized compounds, FG158a, was able to modulate ERK1/2 expression by a CB2R-mediated effect, thus suggesting that this signaling pathway might be involved in its potential anti-cancer effect.

Anti-Inflammatory Activity of a CB2 Selective Cannabinoid Receptor Agonist: Signaling and Cytokines Release in Blood Mononuclear Cells

The endocannabinoid system (ECS) exerts immunosuppressive effects, which are mostly mediated by cannabinoid receptor 2 (CBR2), whose expression on leukocytes is higher than CBR1, mainly localized in the brain. Targeted CBR2 activation could limit inflammation, avoiding CBR1-related psychoactive effects. Herein, we evaluated in vitro the biological activity of a novel, selective and high-affinity CBR2 agonist, called JT11, studying its potential CBR2-mediated anti-inflammatory effect. Trypan Blue and MTT assays were used to test the cytotoxic and anti-proliferative effect of JT11 in Jurkat cells. Its pro-apoptotic activity was investigated analyzing both cell cycle and poly PARP cleavage. Finally, we evaluated its impact on LPS-induced ERK1/2 and NF-kB-p65 activation, TNF-α, IL-1β, IL-6 and IL-8 release in peripheral blood mononuclear cells (PBMCs) from healthy donors. Selective CB2R antagonist SR144528 and CBR2 knockdown were used to further verify the selectivity of JT11. We confirmed selective CBR2 activation by JT11. JT11 regulated cell viability and proliferation through a CBR2-dependent mechanism in Jurkat cells, exhibiting a mild pro-apoptotic activity. Finally, it reduced LPS-induced ERK1/2 and NF-kB-p65 phosphorylation and pro-inflammatory cytokines release in human PBMCs, proving to possess in vitro anti-inflammatory properties. JT11 as CBR2 ligands could enhance ECS immunoregulatory activity and our results support the view that therapeutic strategies targeting CBR2 signaling could be promising for the treatment of chronic inflammatory diseases.

1,8-Naphthyridine Derivatives: A Privileged Scaffold for Versatile Biological Activities

1, 8- Naphthyridine nucleus belongs to significant nitrogen-containing heterocyclic compounds which has garnered the interest of researchers due to its versatile biological activities. It is known to be used as an antimicrobial, anti-psychotic, anti-depressant, anti-convulsant, anti- Alzheimer's, anti-cancer, analgesic, anti-inflammatory, antioxidant, anti-viral, anti-hypertensive, antimalarial, pesticides, anti-platelets, and CB2 receptor agonist, etc. The present review highlights the framework of biological properties of synthesized 1, 8-naphthyridine derivatives developed by various research groups across the globe.

Medicinal Chemistry approach, pharmacology and neuroprotective benefits of CB2R modulators in neurodegenerative diseases

In the last decades, cannabinoid receptor 2 (CB₂R) has continued to receive attention as a key therapeutic target in neuroprotection. Indeed, several findings highlight the neuroprotective effects of CB₂R through suppression of both neuronal excitability and reactive microglia. Additionally, CB₂R seems to be a more promising target than cannabinoid receptor 1 (CB₁R) thanks to the lack of central side effects, its lower expression levels in the central nervous system (CNS), and its inducibility, since its expression enhances quickly in the brain following pathological conditions. This review aims to provide a thorough overview of the main natural and synthetic selective CB₂R modulators, their chemical classification and their potential therapeutic usefulness in neuroprotection, a crucial aspect for the treatment of neurodegenerative diseases.

Preliminary Investigation of a Novel 18F Radiopharmaceutical for Imaging CB2 Receptors in a SOD Mouse Model

We successfully radiolabelled a novel prospective cannabinoid type 2 receptor ligand with 18F and tested its biodistribution in animal models by positron emission tomography (PET)/computed tomography (CT) imaging. The radiolabelling process was conducted on an alkyl mesylate fragment of the main naphthyridine core, using highly efficient microfluidic technology. No preliminary protection was needed, and the product was purified by semi-prep HPLC and SPE formulation, allowing the desired diastereomeric mixture to be obtained in 29% radiochemical yield and>95% radiochemically pure. SOD1G93A mice were used as model of overexpression of CB2 receptors; PET imaging revealed a significant increase of the tracer distribution volume in the brain of symptomatic subjects compared with the asymptomatic ones.

Structure-Activity Relationship of SPOP Inhibitors against Kidney Cancer

Speckle-type POZ protein (SPOP) is overexpressed in the nucleus and misallocated in the cytoplasm in almost all the clear-cell renal cell carcinomas (ccRCCs), which leads to kidney tumorigenesis. Previously, we elucidated that the oncogenic SPOP-signaling pathway in ccRCC could be suppressed by 6b that inhibits SPOP-mediated protein interactions. Herein, we have established a structure-activity relationship for 6b analogues as SPOP inhibitors. Compound 6lc suppresses the viability and inhibits the colony formation of ccRCC cell lines driven by cytoplasmic SPOP, superior to 6b. Compound 6lc binds to the SPOP protein in vitro and disrupts SPOP binding to phosphatase-and-tensin homologue (PTEN) in HEK293T cells, which causes the observable phenomena: a decline in the ubiquitination of PTEN, elevated levels of both PTEN and dual-specificity phosphatase 7, and decreased levels of phosphorylated AKT and ERK when ccRCC cell lines are exposed to 6lc in a dose-response manner. Taken together, compound 6lc is a potent candidate against kidney tumorigenesis.

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.

Development of selective, fluorescent cannabinoid type 2 receptor ligands based on a 1,8-naphthyridin-2-(1H)-one-3-carboxamide scaffold

Cannabinoid type 2 (CB2) receptor has been implicated in several diseases and conditions, however no CB2 receptor selective drugs have made it to market. The aim of this study was to develop fluorescent ligands as CB2 receptor tools, to enable an increased understanding of CB2 receptor expression and signalling and thereby accelerate drug discovery. Fluorescent ligands have been successfully developed for other receptors, however none with adequate subtype selectivity or imaging properties have been reported for CB2 receptor. A series of 1,8-naphthyridin-2-(1H)-one-3-carboxamides with linkers and fluorophores appended in the N1 and C3-positions were developed. Molecular modelling indicated the C3 cis-cyclohexanol-linked compounds directed the linker out of the CB2 receptor between transmembrane helices 1 and 7. Herein we report fluorescent ligand 32 (hCB2 pK i = 6.33 ± 0.02) as one of the highest affinity, selective CB2 receptor fluorescent ligands reported. Despite 32 displaying poor specific labelling of CB2 receptor, the naphthyridine scaffold with this linker remains highly promising for future development of CB2 receptor tools.

Anti-Proliferative Properties and Proapoptotic Function of New CB2 Selective Cannabinoid Receptor Agonist in Jurkat Leukemia Cells

Several studies demonstrated that cannabinoids reduce tumor growth, inhibit angiogenesis, and decrease cancer cell migration. As these molecules are well tolerated, it would be interesting to investigate the potential benefit of newly synthesized compounds, binding cannabinoid receptors (CBRs). In this study, we describe the synthesis and biological effect of 2-oxo-1,8-naphthyridine-3-carboxamide derivative LV50, a new compound with high CB2 receptor (CB2R) affinity. We demonstrated that it decreases viability of Jurkat leukemia cells, evaluated by Trypan Blue and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), but mainly induces a proapoptotic effect. We observed an increase of a hypodiploid peak by propidium iodide staining and changes in nuclear morphology by Hoechst 33258. These data were confirmed by a significant increase of Annexin V staining, cleavage of the nuclear enzyme poly(ADP-ribose)-polymerase (PARP), and caspases activation. In addition, in order to exclude that LV50 non-specifically triggers death of all normal leukocytes, we tested the new compound on normal peripheral blood lymphocytes, excluding the idea of general cytotoxicity. To characterize the involvement of CB2R in the anti-proliferative and proapoptotic effect of LV50, cells were pretreated with a specific CB2R antagonist and the obtained data showed reverse results. Thus, we suggest a link between inhibition of cell survival and proapoptotic activity of the new compound that elicits this effect as selective CB2R agonist.

Chemical Tools for Studying Lipid-Binding Class A G Protein-Coupled Receptors

Cannabinoid, free fatty acid, lysophosphatidic acid, sphingosine 1-phosphate, prostanoid, leukotriene, bile acid, and platelet-activating factor receptor families are class A G protein-coupled receptors with endogenous lipid ligands. Pharmacological tools are crucial for studying these receptors and addressing the many unanswered questions surrounding expression of these receptors in normal and diseased tissues. An inherent challenge for developing tools for these lipid receptors is balancing the often lipophilic requirements of the receptor-binding pharmacophore with favorable physicochemical properties to optimize highly specific binding. In this study, we review the radioligands, fluorescent ligands, covalent ligands, and antibodies that have been used to study these lipid-binding receptors. For each tool type, the characteristics and design rationale along with in vitro and in vivo applications are detailed.

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

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

Design, synthesis and preliminary evaluation of (18)F-labelled 1,8-naphthyridin- and quinolin-2-one-3-carboxamide derivatives for PET imaging of CB2 cannabinoid receptor

In the present work, we report the synthesis of new aryliodonium salts used as precursors of single-stage nucleophilic (18)F radiofluorination. The corresponding unlabelled fluorinated derivatives showed to be CB2 cannabinoid receptor specific ligands, with Ki values in the low nanomolar range and high CB2/CB1 selectivity. The radiolabelled compound [(18)F]CB91, was successfully formulated for in vivo administration, and its preliminary biodistribution was assessed with microPET/CT. This tracer presented a reasonable in vivo stability and a preferential extraction in the tissues that constitutionally express CB2 cannabinoid receptor. The results obtained indicate [(18)F]CB91 as a possible candidate marker of CB2 cannabinoid receptor distribution. This study would open the way to further validation of this tracer for assessing pathologies for which the expression of this receptor is modified.

CB2-selective cannabinoid receptor ligands: synthesis, pharmacological evaluation, and molecular modeling investigation of 1,8-Naphthyridin-2(1H)-one-3-carboxamides

We have recently identified 1,8-naphthyridin-2(1H)-one-3-carboxamide as a new scaffold very suitable for the development of new CB2 receptor potent and selective ligands. In this paper we describe a number of additional derivatives in which the same central scaffold has been variously functionalized in position 1 or 6. All new compounds showed high selectivity and affinity in the nanomolar range for the CB2 receptor. Furthermore, we found that their functional activity is controlled by the presence of the substituents at position C-6 of the naphthyridine scaffold. In fact, the introduction of substituents in this position determined a functionality switch from agonist to antagonists/inverse agonists. Finally, docking studies showed that the difference between the pharmacology of these ligands may be in the ability/inability to block the Toggle Switch W6.48(258) (χ1 g+ → trans) transition.

What we know and do not know about the cannabinoid receptor 2 (CB2)

It has been well appreciated that the endocannabinoid system can regulate immune responses via the cannabinoid receptor 2 (CB2), which is primarily expressed by cells of the hematopoietic system. The endocannabinoid system is composed of receptors, ligands and enzymes controlling the synthesis and degradation of endocannabinoids. Along with endocannabinoids, both plant-derived and synthetic cannabinoids have been shown to bind to and signal through CB2 via G proteins leading to both inhibitory and stimulatory signals depending on the biological process. Because no cannabinoid ligand has been identified that only binds to CB2, the generation of mice deficient in CB2 has greatly expanded our knowledge of how CB2 contributes to immune cell development and function in health and disease. In regards to humans, genetic studies have associated CB2 with a variety of human diseases. Here, we review the endocannabinoid system with an emphasis on CB2 and its role in the immune system.

Synthesis of 3,4-dihydro-1,8-naphthyridin-2(1H)-ones via microwave-activated inverse electron-demand Diels-Alder reactions

Substituted 3,4-dihydro-1,8-naphthyridin-2(1H)-ones have been synthesized with the inverse electron-demand Diels-Alder reaction from 1,2,4-triazines bearing an acylamino group with a terminal alkyne side chain. Alkynes were first subjected to the Sonogashira cross-coupling reaction with aryl halides, the product of which then underwent an intramolecular inverse electron-demand Diels-Alder reaction to yield 5-aryl-3,4-dihydro-1,8-naphthyridin-2(1H)-ones by an efficient synthetic route.

Immune-modulation and properties of absorption and blood brain barrier permeability of 1,8-naphthyridine derivatives

Considering the high selectivity at the cannabinoid CB2 receptor of recently designed 1,8-naphthyridine derivatives and the protective role of this receptor in neurological disorders, in this study we investigated the immune-modulatory and anti-inflammatory effects of these compounds as well as their potential properties of intestinal absorption and blood-brain barrier (BBB) permeability. We used peripheral blood mononuclear cells (PBMC) known to express the CB2 receptor. We observed that test compounds, CB13, CB82 and CB91 reduced PBMC proliferation. The anti-proliferative effect of CB13 and CB91 was partially mediated by the CB2 receptor. These compounds blocked the cells cycle and CB91 reduced T cell activation. CB82 and CB91 down-regulated the expression of phosphorylated proteins like NF-κB, ERK, Akt and the enzyme Cox-2, CB91 blocked the expression of the CB2 receptor and its inhibitory effect was CB2 receptor mediated. We also investigated CB91 properties of intestinal absorption and BBB permeability in order to suggest its potential efficacy on the infiltrating auto-reactive lymphocytes at the level of the central nervous system. For this purpose, CB91 was tested in drug-permeability assays on Caco-2 cells to evaluate its oral bioavailability and on MDCKII-hMDR1 cells to estimate its BBB permeability. The results indicated that this compound possesses medium level of intestinal absorption and BBB permeability. Our data suggest that CB91, modulating the immune response by CB2 receptor mediated mechanism and showing medium level of intestinal absorption and BBB permeability, might be developed as a potential orally delivered drug and might find potential application in pathologies like multiple sclerosis.

Effects on immune cells of a new 1,8-naphthyridin-2-one derivative and its analogues as selective CB2 agonists: implications in multiple sclerosis

The efficacy of cannabinoids in the treatment of multiple sclerosis is widely documented; however their use is limited by psychoactivity mainly ascribed to the activation of the cannabinoid receptor CB1. Emerging findings support as alternative strategy in the treatment of neurodegenerative disorders, the application of compounds targeting the CB2 receptor, since likely unrelated to these side effects. Recently, a novel class of compounds, 1,8-naphthyridine, pyridine and quinoline derivatives have been demonstrated to show high CB2 receptor selectivity and affinity versus the CB1 receptor. Considering that the CB2 receptor is mainly expressed in cell and organs of the immune system, in this study we assessed the potential immune-modulatory effects of these compounds in activated lymphocytes isolated from MS patients with respect to healthy controls. These compounds blocked cell proliferation through a mechanism partially ascribed to the CB2 receptor, down-regulated TNF-α production and did not induce cell death. They also down-regulated Akt, Erk and NF-kB phosphorylation. Despite comparable effects observed in patients and healthy controls, these compounds, in particular, 1,8-naphthyridine and quinoline derivatives inhibited cell activation markers in MS patient derived lymphocytes more efficiently than in healthy control derived cells. Indeed, 1,8-naphthyridin-2-one derivative reduced the levels of Cox-2 in lymphocytes from patients whereas no effect was observed in control cells. Our findings suggest potential application of these drugs in neuro-inflammation, supporting further investigations of the effects of compounds in the therapy of MS, particularly on the aspects regarding activation and inflammation.

Rational design, synthesis and anti-proliferative properties of new CB2 selective cannabinoid receptor ligands: an investigation of the 1,8-naphthyridin-2(1H)-one scaffold

CB2 receptor ligands are becoming increasingly attractive drugs due to the potential role of this receptor in several physiopathological processes. Using our previously described series of 1,8-naphthyridin-2(1H)-on-3-carboxamides as a lead class, several nitrogen heterocyclic derivatives, characterized by different central cores, were synthesized and tested for their affinity toward the human CB1 and CB2 cannabinoid receptors. The obtained results suggest that the new series of quinolin-2(1H)-on-3-carboxamides, 4-hydroxy-2-oxo-1,2-dihydro-1,8-naphthyridine-3-carboxamides and 1,2-dihydro-2-oxopyridine-3-carboxamides represent novel scaffolds very suitable for the development of promising CB2 ligands. Furthermore, the newly synthesized CB2 ligands inhibit proliferation of several cancer cell lines. In particular, it was demonstrated that in DU-145 cell line these ligands exert a CB2-mediated anti-proliferative action and decrease the CB2 receptor expression levels.