Potential of Fatty Acid Amide Hydrolase (FAAH), Monoacylglycerol Lipase (MAGL), and Diacylglycerol Lipase (DAGL) Enzymes as Targets for Obesity Treatment: A Narrative Review

The endocannabinoid system (ECS) plays an integral role in maintaining metabolic homeostasis and may affect hunger, caloric intake, and nutrient absorption. Obesity has been associated with higher levels of the endogenous cannabinoid transmitters (endocannabinoids). Therefore, the ECS is an important target in obesity treatment. Modulating the enzymes that synthesize and degrade endocannabinoids, namely fatty acid amide hydrolase (FAAH), monoacylglycerol lipase (MAGL), and diacylglycerol lipase (DAGL), may be a promising strategy to treat obesity. This review aims to synthesize all studies investigating pharmacological or genetic manipulation of FAAH, MAGL, or DAGL enzymes in association with obesity-related measures. Pharmacological inhibition or genetic deletion of FAAH tended to promote an obesogenic state in animal models, though the relationships between human FAAH polymorphisms and obesity-related outcomes were heterogeneous, which could be due to FAAH having both pro-appetitive and anti-appetitive substrates. Genetic deletion of Mgll and Dagla as well as pharmacological inhibition of DAGL tended to reduce body weight and improve metabolic state in animal studies, though the effects of Mgll manipulation were tissue-dependent. Monitoring changes in body weight in ongoing clinical trials of FAAH inhibitors may clarify whether FAAH inhibition is a potential therapeutic strategy for treatment obesity. More preclinical work is needed to characterize the role of MAGL and DAGL modulation in obesity-related outcomes.

The Novel Monoacylglycerol Lipase Inhibitor MJN110 Suppresses Neuroinflammation, Normalizes Synaptic Composition and Improves Behavioral Performance in the Repetitive Traumatic Brain Injury Mouse Model

Modulation of the endocannabinoid system has emerged as an effective approach for the treatment of many neurodegenerative and neuropsychological diseases. However, the underlying mechanisms are still uncertain. Using a repetitive mild traumatic brain injury (mTBI) mouse model, we found that there was an impairment in locomotor function and working memory within two weeks post-injury, and that treatment with MJN110, a novel inhibitor of the principal 2-arachidononyl glycerol (2-AG) hydrolytic enzyme monoacylglycerol lipase dose-dependently ameliorated those behavioral changes. Spatial learning and memory deficits examined by Morris water maze between three and four weeks post-TBI were also reversed in the drug treated animals. Administration of MJN110 selectively elevated the levels of 2-AG and reduced the production of arachidonic acid (AA) and prostaglandin E2 (PGE2) in the TBI mouse brain. The increased production of proinflammatory cytokines, accumulation of astrocytes and microglia in the TBI mouse ipsilateral cerebral cortex and hippocampus were significantly reduced by MJN110 treatment. Neuronal cell death was also attenuated in the drug treated animals. MJN110 treatment normalized the expression of the NMDA receptor subunits NR2A and NR2B, the AMPA receptor subunits GluR1 and GluR2, and the GABAA receptor subunits α1, β2,3 and γ2, which were all reduced at 1, 2 and 4 weeks post-injury. The reduced inflammatory response and restored glutamate and GABA receptor expression likely contribute to the improved motor function, learning and memory in the MJN110 treated animals. The therapeutic effects of MJN110 were partially mediated by activation of CB1 and CB2 cannabinoid receptors and were eliminated when it was co-administered with DO34, a novel inhibitor of the 2-AG biosynthetic enzymes. Our results suggest that augmentation of the endogenous levels of 2-AG can be therapeutically useful in the treatment of TBI by suppressing neuroinflammation and maintaining the balance between excitatory and inhibitory neurotransmission.

Endocannabinoid Modulation Using Monoacylglycerol Lipase Inhibition in Tourette Syndrome: A Phase 1 Randomized, Placebo-Controlled Study

Introduction Tourette syndrome (TS) is a complex neurodevelopmental disorder characterized by chronic motor and vocal tics. While consistently effective treatment is lacking, evidence indicates that the modulation of endocannabinoid system is potentially beneficial. Lu AG06466 (previously ABX-1431) is a highly selective inhibitor of monoacylglycerol lipase, the primary enzyme responsible for the degradation of the endocannabinoid ligand 2-arachidonoylglycerol. This exploratory study aimed to determine the effect of Lu AG06466 versus placebo on tics and other symptoms in patients with TS. Methods In this phase 1b cross-over study, 20 adult patients with TS on standard-of-care medications were randomized to a single fasted dose of Lu AG06466 (40 mg) or placebo in period 1, followed by the other treatment in period 2. The effects on tics, premonitory urges, and psychiatric comorbidities were evaluated using a variety of scaled approaches at different time points before and after treatment. Results All scales showed an overall trend of tic reduction, with two out of three tic scales (including the Total Tic Score of the Yale Global Tic Severity Score) showing a significant effect of a single dose of Lu AG06466 versus placebo at various timepoints. Treatment with Lu AG06466 resulted in a significant reduction in premonitory urges versus placebo. Single doses of Lu AG06466 were generally well-tolerated, and the most common adverse events were headache, somnolence, and fatigue. Conclusion In this exploratory trial, a single dose of Lu AG06466 showed statistically significant positive effects on key measures of TS symptoms.

Targeting Monoacylglycerol Lipase in Triple Negative Breast Cancer Reduced Tumor-Associated Inflammation, Tumor Growth and Tumor Colonization in the Brain

While the prevalence of breast cancer metastasis in the brain is significantly higher in triple negative breast cancers (TNBCs), there is a lack of novel and/or improved therapies for these patients. Monoacylglycerol lipase (MAGL) is a hydrolase involved in lipid metabolism that catalyzes the degradation of 2-arachidonoylglycerol (2-AG) linked to generation of pro- and anti-inflammatory molecules. Here, we targeted MAGL in TNBCs, using the selective MAGL inhibitor AM9928 (hMAGL IC50 = 9nM, with prolonged pharmacodynamic effects of 46 hours residence time). AM9928 blocked TNBC cell adhesion and transmigration across human brain microvascular endothelial cells (HBMECs) in 3D co-cultures. In addition, AM9928 inhibited the secretion of IL-6, IL-8, and VEGF-A from TNBC cells. TNBC-derived exosomes activated HBMECs resulting in secretion of elevated levels of IL-8 and VEGF, which were inhibited by AM9928. Knockdown of MAGL by siRNA or treatment with AM9928 increased the expression of the adherent junction E-cadherin, known to be regulated by MAGL. Using in vivo studies of syngeneic GFP-4T1-BrM5 mammary tumor cells, AM9928 inhibited tumor growth in the mammary fat pads and attenuated blood brain barrier (BBB) permeability changes, resulting in reduced TNBC colonization in brain. Together, these results support the potential clinical application of MAGL inhibitors as novel treatments for TNBC.

Monoacylglycerol Lipase Inhibition: A Strategy to Treat Chronic Pain in a Humanized Sickle Cell Mouse Model

Introduction: Sickle Cell Disease (SCD) is a major cause of morbidity and mortality worldwide, and affects more than 100,000 people in the US. Acute, vaso-occlusive pain crises are the hallmark of the disease and the primary cause of hospitalization. Recurrent, acute pain episodes compound and result in chronic pain for many patients, though the mechanisms of this transition are poorly understood. Although opioids remain the standard of care to treat SCD chronic pain, their myriad adverse side effects (e.g., constipation, respiratory depression, abuse liability, dependence) as well as the fact that SCD chronic pain requires prolonged opioid treatment that results in tolerance, severely limit their therapeutic utility. Thus, a pressing need exists to identify effective non-opioid analgesic strategies to reduce SCD chronic pain. Humanized mouse models of SCD, such as the Berkeley (BERK) model, provide a useful tool to investigate disease pathophysiology and evaluate novel therapeutic strategies. Dorsal Root Ganglion neurons are peripheral sensory neurons essential for pain preclinical investigations. DRG neurons from rodents in neuropathic pain models show hyperexcitability. Inhibitors of the major degradative enzyme of 2-arachidonoylglycerol, monoacylglycerol lipase (MAGL), reduce nociceptive behavior in neuropathic and inflammatory preclinical models of pain through cannabinoid receptor-dependent and -independent mechanisms. MAGL inhibitors have yet to be tested in BERK mice and we hypothesize that they will ameliorate pain-like behavior and neuronal hyperexcitability. Here we evaluate the effects of MJN110 in a series of pain-related behaviors in BERK mice. Methods: Male and female HbSS-BERK (sickle) and HbAA-BERK (control) mice were used as subjects for these experiments. Pain-like behaviors were assessed using the Von Frey, Hot Plate, and Grip Strength tests. Neuronal hyperexcitability was assessed using whole cell patch clamp electrophysiology of L4-S1 dorsal root ganglia (DRG) neurons. For the dose-response experiments, MJN-110 (1.25, 2.5, 5, and 10 mg/kg, i.p.) was administered one hour prior to testing. Data were analyzed as Student's t-test, one- and two-way ANOVAs followed by Tukey or Sidak post-hoc analysis when appropriate (p < 0.05 considered significant). Results: HbSS-BERK mice displayed profound mechanical allodynia, as well as thermal and deep tissues/musculoskeletal hyperalgesia. HbSS-BERK mice possess extremely hyperexcitable DRG neurons. MJN-110 dose-dependently reduced mechanical allodynia and thermal hyperalgesia in HbSS-BERK mice. Importantly, BERK mice given seven days of daily injections of MJN-110 (5 mg/kg) displayed sustained antinociception that did not undergo tolerance. Ongoing studies are aimed to determine whether MJN110 ameliorates the hyperexcitability of DRG neurons. Conclusion: These initial findings, not only validate that BERK mice show hypersensitive responses to mechanical and heat stimuli, but also demonstrate that neurons innervating the distal parts of BERK mice are hyperexcitable. Additionally, MJN110 reduces these hyper-nociceptive behaviors suggesting that MAGL inhibition represents a viable strategy to reduce chronic pain behaviors in the BERK mouse model. Disclosures Gupta: Tautona Group: Consultancy, Honoraria; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; 1910 Genetics: Other: Grantee; Grifols: Other: Grantee; SCDAA: Membership on an entity's Board of Directors or advisory committees; CSL Behring LLC: Honoraria; NIH: Other: Grantee; University of Minnestoa Foundation: Other: Philanthropic Funding; Southern California Institute for Research and Education Foundation: Other: Philanthropic Funding; Cyclerion: Research Funding; UCI Foundation: Other: Philanthropic Funding. Smith: Emmaus Pharmaceuticals: Consultancy; Global Blood Therapeutics: Consultancy, Honoraria, Research Funding, Speakers Bureau; Novartis Pharmaceuticsl: Consultancy, Honoraria; Novo-Nordisk: Other: DSMB; Pfizer: Consultancy, Research Funding; Imara: Research Funding; Forma Therapeutics: Consultancy, Research Funding; Agios: Research Funding.

Quantification of monoacylglycerol lipase and its occupancy by an exogenous ligand in rhesus monkey brains using [18F]T-401 and PET

Monoacylglycerol lipase (MAGL) is a cytosolic serine hydrolase that cleaves monoacylglycerols into fatty acids and is a potential target for the novel treatment of CNS disorders related to the endocannabinoid system and neuroinflammation. We have developed [18F]T-401 as a selective Positron emission tomography (PET) imaging agent for MAGL. In this study, we determined an analytical method to quantify MAGL availability and its occupancy by an exogenous inhibitor in rhesus monkey brains using [18F]T-401-PET. In rhesus monkeys, regional time-activity curves were described well when using an extended 2-tissue compartment model that accommodated the formation of a radiometabolite in the brain. This model yielded reliable estimates of the total distribution volume ( VT), and the rank order of VT was consistent with known regional activity of MAGL enzyme in primates. The pretreatment of monkeys with JW642 resulted in a dose-dependent reduction of [18F]T-401 retentions in the brain, and VT. Lassen's graphical analysis indicated a VND of 0.69 mL/cm3 and a plasma JW642 concentration of 126 ng/mL for inhibiting the specific binding by 50%. [18F]T-401 and the method established can be used for quantification of MAGL in healthy brain and in disease conditions, and is suitable for evaluations of target engagement at cerebral MAGL.