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Trade names | Lumeron, Memcor |
Other names | LY-246,708 |
Routes of administration | Oral |
Drug class | Muscarinic acetylcholine receptor agonist |
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CompTox Dashboard (EPA) | |
ECHA InfoCard | 100.208.938 |
Chemical and physical data | |
Formula | C14H23N3OS |
Molar mass | 281.42 g·mol−1 |
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Xanomeline (LY-246,708; Lumeron, Memcor) is a small molecule muscarinic acetylcholine receptor agonist that was first synthesized in a collaboration between Eli Lilly and Novo Nordisk as an investigational therapeutic being studied for the treatment of central nervous system disorders. [1] [2]
Its pharmacological action is mediated primarily through stimulation of central nervous system muscarinic M1 and M4 receptor subtypes. [3] [4] Xanomeline is a non-selective muscarinic acetylcholine receptor agonist with similar affinity for all five muscarinic acetylcholine receptor subtypes (Ki = 7–22 nM) but has greater agonistic activity at the M1 and M4 subtypes. [5]
Xanomeline/trospium is an approved [6] combination drug. [7] Trospium chloride is a non-CNS penetrant non-selective muscarinic antagonist to quell peripheral muscarinic agonist-dependent side effects. Xanomeline's mechanism of action is hypothesized to be via rebalancing key neurotransmitter circuits, including acetylcholine, dopamine, and glutamate, which are disrupted in schizophrenia and related diseases. [8]
Xanomeline has structural and pharmacological similarities to the main psychoactive ingredient in betel (areca) nut, arecoline, and the natural muscarinic receptor neurotransmitter, acetylcholine. [1] [2] Xanomeline is an achiral and lipophilic small molecule with a molecular weight of 281.4 (also known as hexyloxy-TZTP, LY246708, Lumeron, Memcor - Eli Lilly; NNC 11-0232 - Novo Nordisk; Kar-XT, Karuna Therapeutics). Xanomeline's physical chemical properties, including low molecular weight, lipophilicity, and absence of hydrogen bond donors, favor its entry into the brain with a high brain to plasma ratio (> 10:1). [3]
Xanomeline is an agonist that primarily targets the muscarinic acetylcholine receptor family of five muscarinic receptor subtypes, which are designated M1-M5. [1] While it binds with near identical affinity to all five of the muscarinic receptor subtypes as measured by displacement of a muscarinic radioligand, the preponderance of evidence suggests that xanomeline acts preferentially in the central nervous system as a functionally selective partial agonist at the M1 and M4 muscarinic receptors. It has more modest partial agonist pharmacology at the M2, M3 and M5 receptors. [9] [10]
Xanomeline may inhibit CYP3A4 and P-glycoprotein locally in the intestines, but does not inhibit them systemically. [5]
CYP2D6 significantly contributes to the metabolism of xanomeline. As a result, CYP2D6 polymorphisms are expected to affect the patient's exposure to xanomeline. [5]
Xanomeline regulates key dopaminergic and glutamatergic circuits in the brain that are thought to be imbalanced in patients suffering from neuropsychiatric and neurological diseases such as schizophrenia and Alzheimer's disease through stimulation primarily of central M1 and M4 muscarinic receptor subtypes. Muscarinic M1 and M4 receptors have been shown in preclinical studies to be expressed in areas important for dopamine and glutamate neural circuit regulation (e.g. frontal cortex and dorsal and ventral striatum,). [8] [11] Xanomeline has shown antipsychotic-like activity in various preclinical behavioral models [8] which is dependent on M1 and M4 receptor activation. [12]
Xanomeline was first discovered in a therapeutic development collaboration between Eli Lilly & Co. and Novo Nordisk pharmaceutical companies in the early 1990s. [2] [3] Eli Lilly led the first clinical development effort of xanomeline through a phase 2 clinical trial to test the hypothesis that it would improve cognition in patients suffering from cognitive decline observed in Alzheimer's disease, with positive results for cognitive decline and an unexpected effect against delusions and hallucination. [13] A small placebo-controlled study in treatment-resistant schizophernia followed, demonstrating its antipsychotic-like action. [14]
Xanomeline's development was discontinued primarily due to cholinergic side effects observed in clinical studies. [15] Further development was enabled through a novel co-formulation strategy, xanomeline/trospium (developmental name KarXT), with the peripherally restricted muscarinic antagonist, trospium, to quell the peripheral cholinergic side effects. [7] In March 2023, Karuna Therapeutics announced that KarXT had met its primary endpoint in a phase III trial, EMERGENT-3, and that it was submitting the drug for approval by the US Food and Drug Administration (FDA). [16] In September 2024, the conbination drug was approved by the FDA. [6]
Acetylcholine (ACh) is an organic compound that functions in the brain and body of many types of animals as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Parts in the body that use or are affected by acetylcholine are referred to as cholinergic.
Muscarine, L-(+)-muscarine, or muscarin is a natural product found in certain mushrooms, particularly in Inocybe and Clitocybe species, such as the deadly C. dealbata. Mushrooms in the genera Entoloma and Mycena have also been found to contain levels of muscarine which can be dangerous if ingested. Muscarine has been found in harmless trace amounts in Boletus, Hygrocybe, Lactarius and Russula. Trace concentrations of muscarine are also found in Amanita muscaria, though the pharmacologically more relevant compound from this mushroom is the Z-drug-like alkaloid muscimol. A. muscaria fruitbodies contain a variable dose of muscarine, usually around 0.0003% fresh weight. This is very low and toxicity symptoms occur very rarely. Inocybe and Clitocybe contain muscarine concentrations up to 1.6%.
Muscarinic acetylcholine receptors, or mAChRs, are acetylcholine receptors that form G protein-coupled receptor complexes in the cell membranes of certain neurons and other cells. They play several roles, including acting as the main end-receptor stimulated by acetylcholine released from postganglionic fibers. They are mainly found in the parasympathetic nervous system, but also have a role in the sympathetic nervous system in the control of sweat glands.
Aceclidine is a parasympathomimetic miotic agent used in the treatment of narrow angle glaucoma.
A muscarinic agonist is an agent that activates the activity of the muscarinic acetylcholine receptor. The muscarinic receptor has different subtypes, labelled M1-M5, allowing for further differentiation.
A muscarinic receptor antagonist (MRA), also called an antimuscarinic, is a type of anticholinergic agent that blocks the activity of the muscarinic acetylcholine receptor. The muscarinic receptor is a protein involved in the transmission of signals through certain parts of the nervous system, and muscarinic receptor antagonists work to prevent this transmission from occurring. Notably, muscarinic antagonists reduce the activation of the parasympathetic nervous system. The normal function of the parasympathetic system is often summarised as "rest-and-digest", and includes slowing of the heart, an increased rate of digestion, narrowing of the airways, promotion of urination, and sexual arousal. Muscarinic antagonists counter this parasympathetic "rest-and-digest" response, and also work elsewhere in both the central and peripheral nervous systems.
The human muscarinic acetylcholine receptor M5, encoded by the CHRM5 gene, is a member of the G protein-coupled receptor superfamily of integral membrane proteins. It is coupled to Gq protein. Binding of the endogenous ligand acetylcholine to the M5 receptor triggers a number of cellular responses such as adenylate cyclase inhibition, phosphoinositide degradation, and potassium channel modulation. Muscarinic receptors mediate many of the effects of acetylcholine in the central and peripheral nervous system. The clinical implications of this receptor have not been fully explored; however, stimulation of this receptor is known to effectively decrease cyclic AMP levels and downregulate the activity of protein kinase A (PKA).
The muscarinic acetylcholine receptor M1, also known as the cholinergic receptor, muscarinic 1, is a muscarinic receptor that in humans is encoded by the CHRM1 gene. It is localized to 11q13.
The muscarinic acetylcholine receptor, also known as cholinergic/acetylcholine receptor M3, or the muscarinic 3, is a muscarinic acetylcholine receptor encoded by the human gene CHRM3.
The muscarinic acetylcholine receptor M4, also known as the cholinergic receptor, muscarinic 4 (CHRM4), is a protein that, in humans, is encoded by the CHRM4 gene.
Vedaclidine (INN, codenamed LY-297,802, NNC 11-1053) is an experimental analgesic drug which acts as a mixed agonist–antagonist at muscarinic acetylcholine receptors, being a potent and selective agonist for the M1 and M4 subtypes, yet an antagonist at the M2, M3 and M5 subtypes. It is orally active and an effective analgesic over 3× the potency of morphine, with side effects such as salivation and tremor only occurring at many times the effective analgesic dose. Human trials showed little potential for development of dependence or abuse, and research is continuing into possible clinical application in the treatment of neuropathic pain and cancer pain relief.
N-Desmethylclozapine (NDMC), or norclozapine, is a major active metabolite of the atypical antipsychotic drug clozapine. Unlike clozapine, it possesses intrinsic activity at the D2/D3 receptors, and acts as a weak partial agonist at these sites similarly to aripiprazole and bifeprunox. Notably, NDMC has also been shown to act as a potent and efficacious agonist at the M1 and δ-opioid receptors, unlike clozapine as well. It was hypothesized that on account of these unique actions, NDMC might underlie the clinical superiority of clozapine over other antipsychotics. However, clinical trials found NMDC itself ineffective in the treatment of schizophrenia. This may be because it possesses relatively low D2/D3 occupancy compared to 5-HT2 (<15% versus 64–79% at a dose of 10–60 mg/kg s.c. in animal studies). Albeit not useful in the treatment of positive symptoms on its own, it cannot be ruled out that NDMC may contribute to the efficacy of clozapine on cognitive and/or negative symptoms.
Tazomeline (LY-287,041) is a drug which acts as a non-selective muscarinic acetylcholine receptor agonist. It was in clinical trials for the treatment of cognitive dysfunction such as that seen in Alzheimer's disease and schizophrenia, but development was apparently scrapped for unknown reasons. Another of the patented uses is for the treatment of "severe painful conditions".
CI-1017 is a muscarinic acetylcholine receptor agonist which is selective for and is approximately equipotent at the M1 and M4 receptors, with 20-30-fold lower affinity for the M2, M3, and M5 subtypes It is the (R)-enantiomer of the racemic compound PD-142,505.
VU-0238429 is a drug which acts as a selective positive allosteric modulator for the muscarinic acetylcholine receptor M5. It was the first selective ligand developed for the M5 subtype, and is structurally derived from older M1-selective positive allosteric modulators such as VU-0119498. Replacing the O-methyl- by a phenyl group further improves the receptor subtype selectivity.
AFDX-384 (BIBN-161) is a drug which acts as a selective antagonist of the muscarinic acetylcholine receptors, with selectivity for the M2 and M4 subtypes. It is used mainly for mapping the distribution of M2 and M4 muscarinic receptors in the brain, and studying their involvement in the development and treatment of dementia and schizophrenia.
Peripherally selective drugs have their primary mechanism of action outside of the central nervous system (CNS), usually because they are excluded from the CNS by the blood–brain barrier. By being excluded from the CNS, drugs may act on the rest of the body without producing side-effects related to their effects on the brain or spinal cord. For example, most opioids cause sedation when given at a sufficiently high dose, but peripherally selective opioids can act on the rest of the body without entering the brain and are less likely to cause sedation. These peripherally selective opioids can be used as antidiarrheals, for instance loperamide (Imodium).
Xanomeline/trospium chloride, sold under the brand name Cobenfy, is a fixed-dose combination medication used for the treatment of schizophrenia. It contains xanomeline, a muscarinic agonist; and trospium chloride, a muscarinic antagonist. Xanomeline is a functionally preferring muscarinic M4 and M1 receptor agonist. Trospium chloride is a non-selective muscarinic antagonist.
Emraclidine is an investigational antipsychotic for the treatment of both schizophrenia and Alzheimer's disease psychosis developed by Cerevel Therapeutics. As of February 2023, it is in phase II of clinical trial. Emraclidine is a positive allosteric modulator that selectively targets the muscarinic acetylcholine receptor M4 subtype. The M4 receptor subtype is expressed in the striatum of the brain, which plays a key role in regulating acetylcholine and dopamine levels. An imbalance of these neurotransmitters has been linked to psychotic symptoms in schizophrenia. Unlike other muscarinic receptors, M4 receptor subtypes are selectively expressed in the striatum and activation of these receptors has been shown to indirectly regulate dopamine levels without blocking D2/D3 receptors, which may lead to unwanted motor side effects seen in current antipsychotics.
12.2 Pharmacodynamics Xanomeline binds to muscarinic receptors M1 to M5 with comparable affinity (Ki=10, 12, 17, 7, and 22 nM for the M1, M2, M3, M4, and M5 receptors, respectively) and exhibits higher agonist activity at the M1 and M4 receptors.