A potent and selective inhibitor for the modulation of MAGL activity in the neurovasculature

Development of a Highly Selective NanoBRET Probe to Assess MAGL Inhibition in Live Cells

Cell-free enzymatic assays are highly useful tools in early compound profiling due to their robustness and scalability. However, their inadequacy to reflect the complexity of target engagement in a cellular environment may lead to a significantly divergent pharmacology that is eventually observed in cells. The discrepancy that emerges from properties like permeability and unspecific protein binding may largely mislead lead compound selection to undergo further chemical optimization. We report the development of a new intracellular NanoBRET assay to assess MAGL inhibition in live cells. Based on a reverse design approach, a highly potent, reversible preclinical inhibitor was conjugated to the cell-permeable BODIPY590 acceptor fluorophore while retaining its overall balanced properties. An engineered MAGL-nanoluciferase (Nluc) fusion protein provided a suitable donor counterpart for the facile interrogation of intracellular ligand activity. Validation of assay conditions using a selection of known MAGL inhibitors set the stage for the evaluation of over 1'900 MAGL drug candidates derived from our discovery program. This evaluation enabled us to select compounds for further development based not only on target engagement, but also on favorable physicochemical parameters like permeability and protein binding. This study highlights the advantages of cell-based target engagement assays for accelerating compound profiling and progress at the early stages of drug discovery programs.

A Highly Selective and Versatile Probe Platform for Visualization of Monoacylglycerol Lipase

Monoacylglycerol lipase (MAGL) is a key enzyme for signal termination in the endocannabinoid system (ECS). MAGL inhibition results in indirect activation of the cannabinoid receptors, which offers unique advantages for the treatment of, e.g., multiple sclerosis, epilepsy, and other neurological disorders. Molecular imaging techniques are valuable tools to overcome the current poor understanding of MAGL's distribution and role in patho- and physiological processes within ECS signaling. Herein, we report the design, synthesis, and validation of highly selective versatile fluorescent and click-chemistry probes for MAGL. Structure-based design combined with a reverse-design approach allowed the development of a structural unit that selectively and effectively recognizes MAGL while offering a versatile platform to attach different fluorophores and further reporter units. In this way, labeled probes with sub-nanomolar potency carrying diverse fluorescent dyes were obtained. Probe affinity and selectivity remained invariant to changes in the fluorophore subunit, showing the remarkable robustness of this platform in delivering tailor-made probes. Highly consistent inhibition across species supports pharmacological model translatability. Extensive profiling and validation in various cellular systems shows the ability of these highly potent and selective probes to elucidate the complex role of MAGL in ECS cellular signaling, inflammatory processes, and disease progression.

Chemical Probes for Investigating the Endocannabinoid System

Cannabis sativa has been used therapeutically since early civilizations, with key cannabinoids Δ9-tetrahydrocannabinol (THC) 3.1 and cannabidiol characterized in the 1960s, leading to the discovery of cannabinoid receptors type 1 (CB1R) and type 2 (CB2R) and the endocannabinoid system (ECS) in the 1990s. The ECS, involving endogenous ligands like 2-arachidonoylglycerol (2-AG) 1.1, anandamide (N-arachidonoylethanolamine (AEA)) 1.2, and various proteins, regulates vital processes such as sleep, appetite, and memory, and holds significant therapeutic potential, especially for neurological disorders. Small molecule-derived pharmacological tools, or chemical probes, target key components of the ECS and are crucial for target validation, mechanistic studies, pathway elucidation, phenotypic screening, and drug discovery. These probes selectively interact with specific proteins or pathways, enabling researchers to modulate target activity and observe biological effects. When they carry an additional reporter group, they are referred to as labeled chemical probes. Developed through medicinal chemistry, structural biology, and high-throughput screening, effective chemical probes must be selective, potent, and depending on their purpose meet additional criteria such as cell permeability and metabolic stability.This chapter describes high-quality labeled and unlabeled chemical probes targeting ECS constituents that have been successfully applied for various research purposes. CB1R and CB2R, class A G protein-coupled receptors, are activated by 2-AG 1.1, AEA 1.2, and THC 3.1, with numerous ligands developed for these receptors. Imaging techniques like single-photon emission computed tomography, positron emission tomography, and fluorescently labeled CB1R and CB2R probes have enhanced CB receptor studies. CB2R activation generally results in immunosuppressive effects, limiting tissue injury. AEA 1.2 is mainly degraded by fatty acid amide hydrolase (FAAH) or N-acylethanolamine acid amidase (NAAA) into ethanolamine and arachidonic acid (AA) 1.3. FAAH inhibitors increase endogenous fatty acid amides, providing analgesic effects without adverse effects. NAAA inhibitors reduce inflammation and pain in animal models. Diacylglycerol lipase (DAGL) is essential for 2-AG 1.1 biosynthesis, while monoacylglycerol lipase (MAGL) degrades 2-AG 1.1 into AA 1.3, thus regulating cannabinoid signaling. Multiple inhibitors targeting FAAH and MAGL have been generated, though NAAA and DAGL probe development lags behind. Similarly, advancements in inhibitors targeting endocannabinoid (eCB) cellular uptake or trafficking proteins like fatty acid-binding proteins have been slower. The endocannabinoidome (eCBome) includes the ECS and related molecules and receptors, offering therapeutic opportunities from non-THC cannabinoids and eCBome mediators. Ongoing research aims to refine chemical tools for ECS and eCBome study, addressing unmet medical needs in central nervous system disorders and beyond.

Structure-Guided Discovery of cis-Hexahydro-pyrido-oxazinones as Reversible, Drug-like Monoacylglycerol Lipase Inhibitors

Monoacylglycerol lipase (MAGL) is a key enzyme involved in the metabolism of the endogenous signaling ligand 2-arachidonoylglycerol, a neuroprotective endocannabinoid intimately linked to central nervous system (CNS) disorders associated with neuroinflammation. In the quest for novel MAGL inhibitors, a focused screening approach on a Roche library subset provided a reversible benzoxazinone hit exhibiting high ligand efficiency. The subsequent design of the three-dimensional cis-hexahydro-pyrido-oxazinone (cis-HHPO) moiety as benzoxazinone replacement enabled the combination of high MAGL potency with favorable ADME properties. Through enzymatic resolution an efficient synthetic route of the privileged cis-(4R,8S) HHPO headgroup was established, providing access to the highly potent and selective MAGL inhibitor 7o. Candidate molecule 7o matches the target compound profile of CNS drugs as it achieves high CSF exposures after systemic administration in rodents. It engages with the target in the brain and modulates neuroinflammatory processes, thus holding great promise for the treatment of CNS disorders.

Pharmacological blockade of 2-AG degradation ameliorates clinical, neuroinflammatory and synaptic alterations in experimental autoimmune encephalomyelitis

The endocannabinoid system (ECS) is critically involved in the pathophysiology of Multiple Sclerosis (MS), a neuroinflammatory and neurodegenerative disease of the central nervous system (CNS). Over the past decade, researchers have extensively studied the neuroprotective and anti-inflammatory effects of the ECS. Inhibiting the degradation of the endocannabinoid 2-arachidonoylglycerol (2-AG) has emerged as a promising strategy to mitigate brain damage in MS. In this study, we investigated the effects of a novel reversible MAGL inhibitor (MAGLi 432) on C57/BL6 female mice with experimental autoimmune encephalomyelitis (EAE), a model of MS. We assessed its implications on motor disability, neuroinflammation, and synaptic dysfunction. Systemic in vivo treatment with MAGLi 432 resulted in a less severe EAE disease, accompanied by increased 2-AG levels and decreased levels of arachidonic acid (AA) and prostaglandins (PGs) in the brain. Additionally, MAGLi 432 reduced both astrogliosis and microgliosis, as evidenced by decreased microglia/macrophage density and a less reactive morphology. Flow cytometry analysis further revealed fewer infiltrating CD45+ and CD3+ cells in the brains of MAGLi 432-treated EAE mice. Finally, MAGLi treatment counteracted the striatal synaptic hyperexcitability promoted by EAE neuroinflammation. In conclusion, MAGL inhibition significantly ameliorated EAE clinical disability and striatal inflammatory synaptopathy through potent anti-inflammatory effects. These findings provide new mechanistic insights into the neuroprotective role of the ECS during neuroinflammation and highlight the therapeutic potential of MAGLi-based drugs in mitigating MS-related inflammatory and neurodegenerative brain damage.

Preclinical Evaluation of the Reversible Monoacylglycerol Lipase PET Tracer (R)-[11C]YH132: Application in Drug Development and Neurodegenerative Diseases

Monoacylglycerol lipase (MAGL) plays a crucial role in the degradation of 2-arachidonoylglycerol (2-AG), one of the major endocannabinoids in the brain. Inhibiting MAGL could lead to increased levels of 2-AG, which showed beneficial effects on pain management, anxiety, inflammation, and neuroprotection. In the current study, we report the characterization of an enantiomerically pure (R)-[11C]YH132 as a novel MAGL PET tracer. It demonstrates an improved pharmacokinetic profile compared to its racemate. High in vitro MAGL specificity of (R)-[11C]YH132 was confirmed by autoradiography studies using mouse and rat brain sections. In vivo, (R)-[11C]YH132 displayed a high brain penetration, and high specificity and selectivity toward MAGL by dynamic PET imaging using MAGL knockout and wild-type mice. Pretreatment with a MAGL drug candidate revealed a dose-dependent reduction of (R)-[11C]YH132 accumulation in WT mouse brains. This result validates its utility as a PET probe to assist drug development. Moreover, its potential application in neurodegenerative diseases was explored by in vitro autoradiography using brain sections from animal models of Alzheimer's disease and Parkinson's disease.