Blocking Alcoholic Steatosis in Mice with a Peripherally Restricted Purine Antagonist of the Type 1 Cannabinoid Receptor.

Type 1 cannabinoid receptor (CB1) antagonists have demonstrated promise for the treatment of obesity, liver disease, metabolic syndrome, and dyslipidemias. However, the inhibition of CB1 receptors in the central nervous system can produce adverse effects, including depression, anxiety, and suicidal ideation. Efforts are now underway to produce peripherally restricted CB1 antagonists to circumvent CNS-associated undesirable effects. In this study, a series of analogues were explored in which the 4-aminopiperidine group of compound 2 was replaced with aryl- and heteroaryl-substituted piperazine groups both with and without a spacer. This resulted in mildly basic, potent antagonists of human CB1 (hCB1). The 2-chlorobenzyl piperazine, 25, was found to be potent ( Ki = 8 nM); to be >1000-fold selective for hCB1 over hCB2; to have no hERG liability; and to possess favorable ADME properties including high oral absorption and negligible CNS penetration. Compound 25 was tested in a mouse model of alcohol-induced liver steatosis and found to be efficacious. Taken together, 25 represents an exciting lead compound for further clinical development or refinement.

Synthesis, Pharmacological Evaluation, and Docking Studies of Novel Pyridazinone-Based Cannabinoid Receptor Type†2 Ligands.

In recent years, cannabinoid type 2 receptors (CB2 R) have emerged as promising therapeutic targets in a wide variety of diseases. Selective ligands of CB2 R are devoid of the psychoactive effects typically observed for CB1 R ligands. Based on our recent studies on a class of pyridazinone 4-carboxamides, further structural modifications of the pyridazinone core were made to better investigate the structure-activity relationships for this promising scaffold with the aim to develop potent CB2 R ligands. In binding assays, two of the new synthesized compounds [6-(3,4-dichlorophenyl)-2-(4-fluorobenzyl)-cis-N-(4-methylcyclohexyl)-3-oxo-2,3-dihydropyridazine-4-carboxamide (2) and 6-(4-chloro-3-methylphenyl)-cis-N-(4-methylcyclohexyl)-3-oxo-2-pentyl-2,3-dihydropyridazine-4-carboxamide (22)] showed high CB2 R affinity, with Ki values of 2.1 and 1.6 nm, respectively. In addition, functional assays of these compounds and other new active related derivatives revealed their pharmacological profiles as CB2 R inverse agonists. Compound 22 displayed the highest CB2 R selectivity and potency, presenting a favorable in silico pharmacokinetic profile. Furthermore, a molecular modeling study revealed how 22 produces inverse agonism through blocking the movement of the toggle-switch residue, W6.48.

Tetrahydropyrazolo[4,3-c]pyridine derivatives as potent and peripherally selective cannabinoid-1 (CB1) receptor inverse agonists.

Peripherally restricted CB1 receptor inverse agonists hold potential as useful therapeutics to treat obesity and related metabolic diseases without causing undesired CNS-mediated adverse effects. We identified a series of tetrahydropyrazolo[4,3-c]pyridine derivatives as potent and highly peripherally selective CB1 receptor inverse agonists. This discovery was achieved by introducing polar functional groups into the molecule, which increase the topological polar surface area and reduce its brain-penetrating ability.

Pharmacokinetic/pharmaco-dynamic modelling and simulation of the effects of different cannabinoid receptor type 1 antagonists on Δ(9)-tetrahydrocannabinol challenge tests.

AIM: The severe psychiatric side effects of cannabinoid receptor type 1 (CB1 ) antagonists hampered their wide development but this might be overcome by careful management of drug development with pharmacokinetic/pharmacodynamic (PK/PD) analyses. PK/PD models suitable for direct comparison of different CB1 antagonists in Δ(9) -tetrahydrocannabinol (THC) challenge tests in healthy volunteer were constructed. METHODS: The pharmacokinetic models of THC and four CB1 antagonists were built separately. THC-induced effects on heart rate and the visual analogue scale of feeling high in healthy volunteers and inhibitive effects of CB1 antagonists on THC-induced effects were modelled in PD models linked to the PK models. Simulations were then applied to evaluate the reduction rate of each antagonist on the reversal of the THC-induced effect in a unified simulation scenario. RESULTS: The final PK model of THC and antagonists was a two compartment model. An Emax model and logistic regression model were used for effect measures and the antagonist effect was added in these models in a competitive binding manner. t1/2ke0 ranged from 0.00462 to 63.7 h for heart rate and from 0.964 to 150 h for VAS. IC50 ranged from 6.42 to 202 ng ml(-1) for heart rate and from 12.1 to 376 ng ml(-1) for VAS. Benchmark simulation showed different dose-efficacy profiles of two efficacy measures for each CB1 antagonist. CONCLUSIONS: PK/PD modelling and simulation approach was suitable for describing and predicting heart rate and feeling high for CB1 antagonists in THC challenge tests. Direct comparison of four antagonists based on simulated efficacy profiles might be of benefit to guide future studies.

Nanoparticle formulation of a poorly soluble cannabinoid receptor 1 antagonist improves absorption by rat and human intestine.

The inclusion of nanoparticles dispersed in a hydrophilic matrix is one of the formulation strategies to improve the bioavailability of orally administered Biopharmaceutics Classification System (BCS) class II and IV drugs by increasing their dissolution rate in the intestine. To confirm that the increased dissolution rate results in increased bioavailability, in vitro and in vivo animal experiments are performed, however, translation to the human situation is hazardous. In this study, we used a range of in vitro and ex vivo methods, including methods applying human tissue, to predict the in vivo oral bioavailability of a model BCS class II CB-1 antagonist, formulated as a nanoparticle solid dispersion. The enhanced dissolution rate from the nanoparticle formulation resulted in an increased metabolite formation in both rat and human precision-cut intestinal slices, suggesting increased uptake and intracellular drug concentration in the enterocytes. In Ussing chamber experiments with human tissue, both the metabolite formation and apical efflux of the metabolite were increased for the nanoparticulate solid dispersion compared with a physical mixture, in line with the results in intestinal slices. The pharmacokinetics of the different formulations was studied in rats in vivo. The nanoparticle formulation indeed improved the absorption of the cannabinoid receptor 1 (CB-1) antagonist and the delivery into the brain compared with the physical mixture. In conclusion, the combined approach provides a valuable set of tools to investigate the effects of formulation on the absorption of poorly soluble compounds in human intestine and may provide relevant information on the oral bioavailability in humans early in the development process.

Peripheral selectivity of the novel cannabinoid receptor antagonist TM38837 in healthy subjects.

AIM: Cannabinoid receptor type 1 (CB1 ) antagonists show central side effects, whereas beneficial effects are most likely peripherally mediated. In this study, the peripherally selective CB1 antagonist TM38837 was studied in humans. METHODS: This was a double-blind, randomized, placebo-controlled, crossover study. On occasions 1-4, 24 healthy subjects received 5 × 4 mg THC with TM38837 100 mg, 500 mg or placebo, or placebos only. During occasion 5, subjects received placebo TM38837 + THC with rimonabant 60 mg or placebo in parallel groups. Blood collections and pharmacodynamic (PD) effects were assessed frequently. Pharmacokinetics (PK) and PD were quantified using population PK-PD modelling. RESULTS: The TM38837 plasma concentration profile was relatively flat compared with rimonabant. TM38837 showed an estimated terminal half-life of 771 h. THC induced effects on VAS feeling high, body sway and heart rate were partly antagonized by rimonabant 60 mg [-26.70% [90% confidence interval (CI) -40.9, -12.6%]; -7.10%, (90%CI -18.1, 5.3%); -7.30%, (90% CI -11.5%, -3.0%) respectively] and TM38837 500 mg [-22.10% (90% CI -34.9, -9.4%); -12.20% (90% CI -21.6%, -1.7%); -8.90% (90% CI -12.8%, -5.1%) respectively]. TM38837 100 mg had no measurable feeling high or body sway effects and limited heart rate effects. CONCLUSIONS: Rimonabant showed larger effects than TM38837, but the heart rate effects were similar. TM38837 100 mg had no impact on CNS effects, suggesting that this dose does not penetrate the brain. This TM38837 dose is predicted to be at least equipotent to rimonabant with regard to metabolic disorders in rodent models. These results provide support for further development of TM38837 as a peripherally selective CB1 antagonist for indications such as metabolic disorders, with a reduced propensity for psychiatric side effects.

Pain as a reward: changing the meaning of pain from negative to positive co-activates opioid and cannabinoid systems.

Pain is a negative emotional experience that is modulated by a variety of psychological factors through different inhibitory systems. For example, endogenous opioids and cannabinoids have been found to be involved in stress and placebo analgesia. Here we show that when the meaning of the pain experience is changed from negative to positive through verbal suggestions, the opioid and cannabinoid systems are co-activated and these, in turn, increase pain tolerance. We induced ischemic arm pain in healthy volunteers, who had to tolerate the pain as long as possible. One group was informed about the aversive nature of the task, as done in any pain study. Conversely, a second group was told that the ischemia would be beneficial to the muscles, thus emphasizing the usefulness of the pain endurance task. We found that in the second group pain tolerance was significantly higher compared to the first one, and that this effect was partially blocked by the opioid antagonist naltrexone alone and by the cannabinoid antagonist rimonabant alone. However, the combined administration of naltrexone and rimonabant antagonized the increased tolerance completely. Our results indicate that a positive approach to pain reduces the global pain experience through the co-activation of the opioid and cannabinoid systems. These findings may have a profound impact on clinical practice. For example, postoperative pain, which means healing, can be perceived as less unpleasant than cancer pain, which means death. Therefore, the behavioral and/or pharmacological manipulation of the meaning of pain can represent an effective approach to pain management.

The bioisosteric concept applied to cannabinoid ligands.

Bioisosterism is widely used in medicinal chemistry as an approach aimed at either rationally modifying a hit compound into a more potent and/or selective molecule or a lead compound into a more drug-like one. Two different cannabinoid receptors have been cloned from mammalian tissues, the CB1 receptor, mostly expressed in brain, and the CB2 receptor, mostly expressed in the immune system, both regulating a variety of physiological functions. Synthetic cannabinoids have been developed that act as highly selective agonists or antagonists/inverse agonists at one or other of these receptor types with the ultimate goal of modulating the endocannabinoid system. This review takes into account the use of the bioisosteric substitution in the field of cannabinoid ligands as a tool for improving both their pharmacodynamic and pharmacokinetic properties.

Rimonabant en el tratamiento de la diabetes tipo 2. Nuevas evidencias / Rimonabant in the treatment of diabetes type 2: new evidence

El descubrimiento de los receptores cannabinoides y de sus ligandos endógenos, los endocannabinoides, ha permitido mejorar el conocimiento de diversos procesos fisiológicos y ha abierto perspectivas terapéuticas de gran interés. Estudios recientes han esclarecido el papel crucial que desempeña el sistema endocannabinoide en el control de la ingesta alimentaria y el metabolismo a través de los receptores CB1. La activación de dichos receptores promueve la ingesta y produce una amplia gama de acciones metabólicas independientes dirigidas a obtener una acumulación de energía. Estas acciones tienen lugar en los principales órganos periféricos encargados de la regulación del metabolismo, incluyendo el tejido adiposo, el hígado, el músculo esquelético y el páncreas. Los resultados obtenidos recientemente en los diferentes ensayos clínicos realizados con rimonabant, el primer antagonista del receptor CB1, sugieren un futuro prometedor para esta nueva generación de fármacos que actúan en una diana farmacológica emergente para el tratamiento de la diabetes tipo 2 y el manejo global del conjunto de factores de riesgo cardiometabólico. Los ensayos clínicos actualmente en desarrollo permitirán determinar el alcance terapéutico a largo plazo de los efectos beneficiosos que rimonabant induce sobre el metabolismo. Esta revisión recoge los hallazgos recientes que han permitido definir el papel que desempeña el sistema endocannabinoide en el control del equilibrio energético y del metabolismo lipídico e hidrocarbonado, y expone las perspectivas terapéuticas innovadoras que se han abierto con el desarrollo de los antagonistas selectivos de los receptores cannabinoides CB1, concretamente en el paciente con diabetes tipo 2 (AU)

The discovery of the cannabinoid receptors and their endogenous ligands, the endocannabinoids, has increased the knowledge of a number of physiological processes and has opened new therapeutic perspectives of interest. Recent studies have clarified the crucial role of the endocannabinoid system in controlling food intake and metabolism by means of the CB1 receptors. CB1 receptor activation promotes food intake and produces a wide range of independent metabolic actions leading to energy accumulation. These actions take place in the major peripheral organs responsible for the regulation of metabolism, including adipose tissue, liver, skeletal muscle and pancreas. Recent findings in various clinical trials with rimonabant, the first CB1 receptor antagonist, suggest a promising future forthis new generation of drugs that act on an emerging pharmacological target for the treatment of type 2 diabetes and the overall management of all cardiometabolic risk factors. Clinical trials currently under development will determine the long-term therapeutic impact of the beneficial effects on metabolism induced by rimonabant. This review reflects the recent findings that have clarified the role of the endocannabinoid system in controlling energy balance and lipid and carbohydrate metabolism, and discusses novel therapeutic perspectives that have been introduced with the development of selective antagonists of the cannabinoid CB1 receptors, specifically in type 2 diabetic patients (AU)