Methocinnamox (MCAM) is an

opioid receptor antagonist An opioid antagonist, or opioid receptor antagonist, is a receptor antagonist that acts on one or more of the opioid receptors. Naloxone and naltrexone are commonly used opioid antagonist drugs which are competitive antagonists that bind to the ...

. It is a pseudo-irreversible

non-competitive Non-competitive inhibition is a type of enzyme inhibition where the inhibitor reduces the activity of the enzyme and binds equally well to the enzyme regardless of whether it has already bound the substrate. This is unlike competitive inhibition, ...

antagonist An antagonist is a character in a story who is presented as the main enemy or rival of the protagonist and is often depicted as a villain.μ-opioid receptor The μ-opioid receptors (MOR) are a class of opioid receptors with a high affinity for enkephalins and beta-endorphin, but a low affinity for dynorphins. They are also referred to as μ(''mu'')-opioid peptide (MOP) receptors. The prototypical ...

and a

competitive antagonist A receptor antagonist is a type of receptor ligand or drug that blocks or dampens a biological response by binding to and blocking a receptor rather than activating it like an agonist. Antagonist drugs interfere in the natural operation of recep ...

of the κ- and

δ-opioid receptor The δ-opioid receptor, also known as delta opioid receptor or simply delta receptor, abbreviated DOR or DOP, is an inhibitory 7-transmembrane G-protein coupled receptor coupled to the G protein Gi alpha subunit, Gi/G0 and has enkephalins as it ...

s. The drug has a very long

duration of action Pharmacodynamics (PD) is the study of the biochemical and physiologic effects of drugs (especially pharmaceutical drugs). The effects can include those manifested within animals (including humans), microorganisms, or combinations of organisms (fo ...

of up to months with a single dose due to its pseudo-irreversibility. It is administered in animals by

intravenous Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutr ...

subcutaneous injection Subcutaneous administration is the insertion of medications beneath the skin either by injection or infusion. A subcutaneous injection is administered as a bolus (medicine), bolus into the subcutis, the layer of skin directly below the dermis and ...

. It was first described in the

scientific literature Scientific literature encompasses a vast body of academic papers that spans various disciplines within the natural and social sciences. It primarily consists of academic papers that present original empirical research and theoretical ...

in 2000. It has not been studied in humans as of 2022. There is interest in methocinnamox in the potential treatment of

opioid use disorder Opioid use disorder (OUD) is a substance use disorder characterized by cravings for opioids, continued use despite physical and/or psychological deterioration, increased tolerance with use, and withdrawal symptoms after discontinuing opioids. ...

and

opioid overdose An opioid overdose is toxicity due to excessive consumption of opioids, such as morphine, codeine, heroin, fentanyl, tramadol, and methadone. This preventable pathology can be fatal if it leads to respiratory depression, a lethal conditio ...

due to its much longer-lasting and insurmountable effects relative to other opioid antagonists like

naloxone Naloxone, sold under the brand name Narcan among others, is an opioid antagonist, a medication used to reverse or reduce the effects of opioids. For example, it is used to restore breathing after an opioid overdose. Effects begin within two ...

and

naltrexone Naltrexone, sold under the brand name Revia among others, is a medication primarily used to manage alcohol use or opioid use disorder by reducing cravings and feelings of euphoria associated with substance use disorder. It has also been ...

Clinical trial Clinical trials are prospective biomedical or behavioral research studies on human subject research, human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel v ...

s of the drug are expected. Methocinnamox should not be confused with methoclocinnamox (MCCAM), which is a closely related but structurally different

compound Compound may refer to: Architecture and built environments * Compound (enclosure), a cluster of buildings having a shared purpose, usually inside a fence or wall ** Compound (fortification), a version of the above fortified with defensive struc ...

(

chlorine Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...

instead of

methyl In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula (whereas normal methane has the formula ). In formulas, the group is often abbreviated as ...

on one of the

benzene Benzene is an Organic compound, organic chemical compound with the Chemical formula#Molecular formula, molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal Ring (chemistry), ring with one hyd ...

ring (The) Ring(s) may refer to: * Ring (jewellery), a round band, usually made of metal, worn as ornamental jewelry * To make a sound with a bell, and the sound made by a bell Arts, entertainment, and media Film and TV * ''The Ring'' (franchise), a ...

s). The drug was derived via

structural modification Molecular modification is chemical alteration of a known and previously characterized lead compound for the purpose of enhancing its usefulness as a drug. This could mean enhancing its specificity for a particular body target site, increasing its ...

buprenorphine Buprenorphine, sold under the brand name Subutex among others, is an opioid used to treat opioid use disorder, acute pain, and chronic pain. It can be used under the tongue (sublingual), in the cheek (buccal), by injection (intravenous a ...

Pharmacology

Pharmacodynamics

Methocinnamox is an

, it works at the

μ-opioid receptor The μ-opioid receptors (MOR) are a class of opioid receptors with a high affinity for enkephalins and beta-endorphin, but a low affinity for dynorphins. They are also referred to as μ(''mu'')-opioid peptide (MOP) receptors. The prototypical ...

. By acting as an antagonist, it binds to the receptor but does not activate it, thus blocking the action of agonists such as

heroin Heroin, also known as diacetylmorphine and diamorphine among other names, is a morphinan opioid substance synthesized from the Opium, dried latex of the Papaver somniferum, opium poppy; it is mainly used as a recreational drug for its eupho ...

and

fentanyl Fentanyl is a highly potent synthetic piperidine opioid primarily used as an analgesic (pain medication). It is 30 to 50 times more Potency (pharmacology), potent than heroin and 50 to 100 times more potent than morphine. Its primary Medici ...

. It is a pseudo-irreversible

antagonist An antagonist is a character in a story who is presented as the main enemy or rival of the protagonist and is often depicted as a villain.competitive antagonist A receptor antagonist is a type of receptor ligand or drug that blocks or dampens a biological response by binding to and blocking a receptor rather than activating it like an agonist. Antagonist drugs interfere in the natural operation of recep ...

of the κ- and

s. Methocinnamox has

affinity Affinity may refer to: Commerce, finance and law * Affinity (law), kinship by marriage * Affinity analysis, a market research and business management technique * Affinity Credit Union, a Saskatchewan-based credit union * Affinity Equity Pa ...

values for the

opioid receptor Opioid receptors are a group of inhibitory G protein-coupled receptors with opioids as ligands. The endogenous opioids are dynorphins, enkephalins, endorphins, endomorphins and nociceptin. The opioid receptors are ~40% identical to somatostati ...

s of 0.6nM for the μ-opioid receptor, 2.2nM for the δ-opioid receptor, and 4.9nM for the κ-opioid receptor. Hence, it has about 3.7-fold preferential affinity for the μ-opioid receptor over the δ-opioid receptor and about 8.2-fold higher affinity for the μ-opioid receptor over the κ-opioid receptor. The antagonism of the μ-opioid receptor by methocinnamox is not irreversible as the drug does not form a

covalent bond A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atom ...

with the receptor. This is in contrast to prototypical μ-opioid receptor

alkylating agent Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting ...

s like

β-funaltrexamine β-Funaltrexamine (β-FNA) is an irreversible ( covalently bonding) opioid antagonist that was used to create the first crystal structure of the μ-opioid receptor (MOR). It is selective for antagonism of the MOR over the δ-opioid receptor ( ...

and

β-chlornaltrexamine β-Chlornaltrexamine (β-CNA) is a non-selective irreversible antagonist of the μ-opioid receptor (MOR), the δ-opioid receptor (DOR), and the κ-opioid receptor (KOR), which forms a covalent bond to the binding sites of these receptors and ha ...

. However, in spite of its lack of covalent binding to the μ-opioid receptor, methocinnamox appears to not dissociate from the μ-opioid receptor or dissociates from it extremely slowly. Hence, methocinnamox has been described as a pseudo-irreversible antagonist of the μ-opioid receptor or as a "functionally irreversible" antagonist. The mechanism underlying the pseudo-irreversible antagonism of methocinnamox hasn't been fully elucidated. Also unlike irreversible μ-opioid receptor antagonists like β-funaltrexamine and β-chlornaltrexamine, methocinnamox lacks κ-opioid receptor agonism and is more selective for the μ-opioid receptor in its actions. Methocinnamox has been found to bind to two distinct sites on the μ-opioid receptor. It binds to the

orthosteric site In the fields of biochemistry and pharmacology an allosteric regulator (or allosteric modulator) is a substance that binds to a site on an enzyme or receptor distinct from the active site, resulting in a conformational change that alters the p ...

as a pseudo-irreversible and non-competitive antagonist, thereby directly blocking opioid binding. In addition, methocinnamox has been found to bind to and act as an antagonist of an unknown

allosteric site In the fields of biochemistry and pharmacology an allosteric regulator (or allosteric modulator) is a substance that binds to a site on an enzyme or receptor distinct from the active site, resulting in a conformational change that alters the p ...

on the μ-opioid receptor with lower affinity that modulates the affinity and/or

intrinsic activity Intrinsic activity (IA) and efficacy (Emax) refer to the relative ability of a drug- receptor complex to produce a maximum functional response. This must be distinguished from the affinity, which is a measure of the ability of the drug to bind ...

of orthosteric μ-opioid receptor agonists. The μ-opioid receptor antagonism of methocinnamox is non-competitive and insurmountable by μ-opioid receptor agonists like

morphine Morphine, formerly also called morphia, is an opiate that is found naturally in opium, a dark brown resin produced by drying the latex of opium poppies (''Papaver somniferum''). It is mainly used as an analgesic (pain medication). There are ...

and fentanyl. It has been found to completely block the effects of morphine at morphine doses of up to 1,000mg/kg in animals, with the dose–response curve of morphine being shifted rightward by up to 100-fold. Doses of morphine of 1,000mg/kg are normally often fatal. The insurmountability of methocinnamox's μ-opioid receptor antagonism is in contrast to that with competitive μ-opioid receptor antagonists like

and

, which can be overcome with higher doses of μ-opioid receptor agonists. In contrast to the μ-opioid receptor, the antagonism of the κ- and δ-opioid receptors by methocinnamox is competitive and reversible. Moreover, methocinnamox shows a short duration in the body. The actions of methocinnamox ''

in vivo Studies that are ''in vivo'' (Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, an ...

'' are selective for μ-opioid receptor antagonism, with a lack of significant antagonism of the effects of κ-opioid receptor agonists like bremazocine or δ-opioid receptor agonists like

BW373U86 (+)-BW373U86 is an opioid analgesic drug used in scientific research. BW373U86 is a selective agonist for the δ-opioid receptor, with approximately 15× stronger affinity for the δ-opioid than the μ-opioid receptor. It has potent analgesic ...

. The actions of methocinnamox are dose-dependent. A single dose of 3.2mg/kg blocked the effects of morphine for approximately 2weeks in animals whereas a single 10mg/kg dose blocked the effects of morphine for over 2months.

Pharmacokinetics

In animals, methocinnamox reached

peak Peak or The Peak may refer to: Basic meanings Geology * Mountain peak ** Pyramidal peak, a mountaintop that has been sculpted by erosion to form a point Mathematics * Peak hour or rush hour, in traffic congestion * Peak (geometry), an (''n''-3)-d ...

concentrations 15 to 45minutes following

injection Injection or injected may refer to: Science and technology * Injective function, a mathematical function mapping distinct arguments to distinct values * Injection (medicine), insertion of liquid into the body with a syringe * Injection, in broadca ...

and had an

elimination half-life Biological half-life (elimination half-life, pharmacological half-life) is the time taken for concentration of a biological substance (such as a medication) to decrease from its maximum concentration ( Cmax) to half of Cmax in the blood plasma. ...

of approximately 70minutes. In spite of this short duration in the body however, the μ-opioid receptor antagonist effects of methocinnamox persist for up to months with a single injection. These findings suggest that the long-lasting effects of methocinnamox are not due to

pharmacokinetic Pharmacokinetics (from Ancient Greek ''pharmakon'' "drug" and ''kinetikos'' "moving, putting in motion"; see chemical kinetics), sometimes abbreviated as PK, is a branch of pharmacology dedicated to describing how the body affects a specific subs ...

factors but rather its

pharmacodynamic Pharmacodynamics (PD) is the study of the biochemistry, biochemical and physiology, physiologic effects of drugs (especially pharmaceutical drugs). The effects can include those manifested within animals (including humans), microorganisms, or comb ...

properties and pseudo-irreversible antagonism.

Chemistry

In terms of

chemical structure A chemical structure of a molecule is a spatial arrangement of its atoms and their chemical bonds. Its determination includes a chemist's specifying the molecular geometry and, when feasible and necessary, the electronic structure of the target m ...

, methocinnamox is a cinnamoyl

amido Azanide is the IUPAC-sanctioned name for the anion . The term is obscure; derivatives of are almost invariably referred to as amides, despite the fact that amide also refers to the organic functional group –. The anion is the conjugate base ...

morphinan Morphinan is the prototype chemical structure of a large chemical class of psychoactive drugs, consisting of opiate analgesics, cough suppressants, and dissociative hallucinogens, among others. Typical examples include compounds such as morphine, ...

and is closely related to clocinnamox and methoclocinnamox. It was derived via

History

Clocinnamox was first described in the

by 1992. Methoclocinnamox, which is metabolically converted into clocinnamox and is a

partial agonist In pharmacology, partial agonists are drugs that bind to and activate a given Receptor (biochemistry), receptor, but have only partial Intrinsic activity, efficacy at the receptor relative to a full agonist. They may also be considered Ligand (bio ...

, was first described by 1995. Methocinnamox was first described in 2000.

Research

Opioid overdose and/or opioid use disorder

Methocinnamox is able to reverse the

respiratory depressant Hypoventilation (also known as respiratory depression) occurs when ventilation is inadequate (''hypo'' meaning "below") to perform needed respiratory gas exchange. By definition it causes an increased concentration of carbon dioxide (hypercapnia ...

effects of

and

in animals. However, unlike

, another

opioid antagonist An opioid antagonist, or opioid receptor antagonist, is a receptor antagonist that acts on one or more of the opioid receptors. Naloxone and naltrexone are commonly used opioid antagonist drugs which are competitive antagonists that bind to ...

, its action lasts around 2weeks if administered

subcutaneously The subcutaneous tissue (), also called the hypodermis, hypoderm (), subcutis, or superficial fascia, is the lowermost layer of the integumentary system in vertebrates. The types of cells found in the layer are fibroblasts, adipose cells, and m ...

and up to 5days if administered

intravenously Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutr ...

. This could make it a better

antidote An antidote is a substance that can counteract a form of poisoning. The term ultimately derives from the Greek term φάρμακον ἀντίδοτον ''(pharmakon antidoton)'', "(medicine) given as a remedy". An older term in English which is ...

than naloxone in

s, because naloxone usually lasts around 30minutes, there is a need for repeated administration and a danger of renarcotization. By acting longer, methocinnamox prevents these dangers. Methocinnamox has not yet been tested in humans as of 2022. However, it has been tested in rodents and monkeys. It was reported in March 2020 that

clinical trial Clinical trials are prospective biomedical or behavioral research studies on human subject research, human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel v ...

s of methocinnamox were expected to begin within 18 to 24months. In March 2023, it was reported that a phase 1 clinical trial of methocinnamox funded by the

National Institutes of Health The National Institutes of Health (NIH) is the primary agency of the United States government responsible for biomedical and public health research. It was founded in 1887 and is part of the United States Department of Health and Human Service ...

(NIH) would possibly start in 2024.

References

{{Opioid receptor modulators 4,5-Epoxymorphinans Carboxamides Cyclic ketones Cyclopropyl compounds Experimental drugs Heterocyclic compounds with 5 rings Hydroxyarenes Mu-opioid receptor antagonists Nitrogen heterocycles Opioid receptor negative allosteric modulators Oxygen heterocycles