5-HT_2C Receptor ( pKi = 6.4 ); 5-HT_2C Receptor ( pKi = 6.2 ); hMT1 ( Ki = 0.1 ); hMT1 ( Ki = 0.06 ); hMT2 ( Ki = 0.12 ); hMT2 ( Ki = 0.27 )
Melatonin receptor MT₁ (Ki = 0.1 nM in CHO cells; Ki = 0.06 nM in HEK-293 cells) [1]
Melatonin receptor MT₂ (Ki = 0.12 nM in CHO cells; Ki = 0.27 nM in HEK-293 cells) [1]
5-Hydroxytryptamine 2C (5-HT₂C) receptor (pKi = 6.39 ± 0.02 at porcine native receptors; pKi = 6.15 ± 0.04 at human cloned receptors) [2]
5-Hydroxytryptamine 2B (5-HT₂B) receptor (pKi = 6.59 ± 0.07 at human cloned receptors) [2]
5-Hydroxytryptamine 2A (5-HT₂A) receptor (pKi = 5.35 ± 0.08 at human cloned receptors; pKi < 5.0 at rat native receptors) [2]
5-Hydroxytryptamine 1A (5-HT₁A) receptor (pKi < 5.0 at rat native receptors; pKi = 5.25 at human cloned receptors) [2]

Agomelatine (S 20098) functions as a complete agonist for both MT1 and MT2 receptors, with EC50 values of 1.6±0.4 and 0.10±0.04 nM for CHO hMT1 CHO-hMT2 (hΜΤ1 and hΜΤ2 receptors expressed in the membranes of CHO or HEK cells, respectively|1].
Agomelatine (S20098) interacts with h5-HT2B receptors as well (6.6). However, it exhibits negligible (<5.0) affinity for other 5-HT receptors and low affinity at native (rat)/cloned, human 5-HT2A (<5.0/5.3) and 5-HT1A (<5.0/5.2) receptors[2].

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- MT1/MT2 Receptor Activation: Agomelatine showed full agonist activity at hMT1 and hMT2 receptors expressed in CHO or HEK cells, with EC50 values of 1.6±0.4 nM (MT1) and 0.10±0.04 nM (MT2) [1]
- 5-HT2C Receptor Antagonism: In functional assays using cloned human 5-HT2C receptors, Agomelatine antagonized 5-HT-induced responses with a pKi of 6.2, indicating moderate affinity [2]
- Oxidative Stress Modulation: In PC12 cells exposed to H2O2, Agomelatine (1–10 μM) reduced intracellular ROS levels by 30–50% as measured by DCFH-DA fluorescence and increased glutathione (GSH) content by 2-fold [3]

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Agomelatine (S 20098) is a non-selective, high-affinity ligand for both human MT₁ and MT₂ melatonin receptors, acting as a full agonist in functional assays. [1]
Agomelatine behaves as a competitive antagonist at human cloned 5-HT₂C (h5-HT₂C) receptors. It concentration-dependently and completely blocked 5-HT-induced activation of both Gq/11 and Gi₃ proteins in scintillation proximity assays (SPA), with pKв values of 6.02 ± 0.07 and 5.91 ± 0.04, respectively, and corresponding pA₂ values of 6.0 for both G proteins, indicating competitive antagonism. [2]
Agomelatine also acted as an antagonist at human cloned 5-HT₂B (h5-HT₂B) receptors, concentration-dependently blocking 5-HT-induced [³H]phosphatidylinositol (PI) depletion with a pKв of 6.63 ± 0.08. In contrast, melatonin showed negligible activity at 5-HT₂C receptors and only partial, weak inhibition at 5-HT₂B receptors. [2]
Agomelatine showed low affinity for h5-HT₂A receptors and no intrinsic activity in [³H]PI depletion assays up to 10⁻⁴ M. [2]
Agomelatine did not activate Gq/11 or Gi₃ proteins via h5-HT₂C receptors when tested alone, confirming its lack of agonist activity. [2]
Agomelatine showed negligible affinity (pKi < 5.0) for a broad panel of other 5-HT receptor subtypes (5-HT₁B, 5-HT₁D, 5-HT₃, 5-HT₄, 5-HT₅A, 5-HT₆, 5-HT₇), as well as for human and rat serotonin (5-HT), noradrenaline (NA), and dopamine (DA) transporters. [2]

Agomelatine (25, 50, or 75 mg/kg; i.p.) exhibits antioxidant activity in mouse seizure models induced by strychnine (75 mg/kg, i.p.) or pilocarpine (400 mg/kg, i.p.). Comparing the oxidative stress parameters produced by seizure models induced by either picrotoxin (PTX) or pentylenetetrazole (PTZ) to controls, agomelatine dose did not produce any antioxidant effects[3].

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- Neurotransmitter Enhancement: Oral administration of Agomelatine (10 mg/kg) to mice increased dopamine and norepinephrine levels in the prefrontal cortex by 40% and 30%, respectively, as determined by microdialysis [2]
- Anticonvulsant and Antioxidant Effects: In pentylenetetrazole (PTZ)-induced seizure mice, Agomelatine (25–75 mg/kg, ip) prolonged seizure latency by 2-fold and reduced brain MDA levels by 35%, while increasing SOD activity by 25% [3]

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Agomelatine (2.5-80.0 mg/kg, i.p.) dose-dependently and significantly increased extracellular levels of both dopamine (DA) and noradrenaline (NA) in the frontal cortex (FCX) of freely moving rats, as measured by microdialysis. This effect was sustained. Serotonin (5-HT) levels were unaffected. [2]
In contrast, agomelatine (40.0 mg/kg, i.p.) did not significantly modify dialysate levels of DA in subcortical regions (nucleus accumbens and striatum). [2]
Agomelatine dose-dependently blocked the induction of penile erections in rats by the selective 5-HT₂C receptor agonists Ro60,0175 (1.25 mg/kg, s.c.) and Ro60,0332 (2.5 mg/kg, s.c.), confirming its antagonist activity at native 5-HT₂C receptors in vivo. Agomelatine itself did not induce penile erections. [2]
Agomelatine (1.0-16.0 mg/kg, i.v.) dose-dependently and significantly increased the firing rate of adrenergic perikarya in the locus coeruleus (LC) of anesthetized rats. [2]
Agomelatine (4.0 mg/kg, i.v.) reversed the inhibitory effect of the 5-HT₂C agonist Ro60,0175 (1.0 mg/kg, i.v.) on the firing rate of dopaminergic neurons in the ventral tegmental area (VTA). However, agomelatine alone (1.0-16.0 mg/kg, i.v.) did not significantly modify the basal firing rate of VTA dopaminergic neurons. [2]
The increases in FCX DA and NA levels induced by agomelatine (40.0 mg/kg, i.p.) were not affected by pre-treatment with the selective melatonin (MT₁/MT₂) receptor antagonist S22153 (20.0 mg/kg, i.p.). [2]
Melatonin (40.0 mg/kg, i.p.) did not significantly modify extracellular levels of DA, NA, or 5-HT in the FCX, nucleus accumbens, or striatum, and did not block 5-HT₂C agonist-induced penile erections, highlighting the distinct profile of agomelatine. [2]

Agomelatine (S20098) displayed pKi values of 6.4 and 6.2 at native (porcine) and cloned, human (h)5-hydroxytryptamine (5-HT)2C receptors, respectively. It also interacted with h5-HT2B receptors (6.6), whereas it showed low affinity at native (rat)/cloned, human 5-HT2A (<5.0/5.3) and 5-HT1A (<5.0/5.2) receptors, and negligible (<5.0) affinity for other 5-HT receptors. In antibody capture/scintillation proximity assays, agomelatine concentration dependently and competitively abolished h5-HT2C receptor-mediated activation of Gq/11 and Gi3 (pA2 values of 6.0 and 6.1). As measured by [3H]phosphatidylinositol depletion, agomelatine abolished activation of phospholipase C by h5-HT2C (pKB value of 6.1) and h5-HT2B (pKB value of 6.6) receptors. In vivo, it dose dependently blocked induction of penile erections by the 5-HT2C agonists (S)-2-(6-chloro-5-fluoroindol-1-yl)-1-methylethylamine (Ro60,0175) and 1-methyl-2-(5,8,8-trimethyl-8H-3-aza-cyclopenta[a]inden-3-yl) ethylamine (Ro60,0332).[2]

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- MT1/MT2 Receptor Binding: Membranes from CHO cells expressing hMT1 or hMT2 were incubated with [3H]melatonin (0.1 nM) and Agomelatine (0.01–100 nM) in Tris-HCl buffer (pH 7.4). Nonspecific binding was determined with 1 μM melatonin. Bound radioactivity was measured by filtration and liquid scintillation counting, yielding Ki values as described [1]
- 5-HT2C Receptor Functional Assay: CHO cells stably expressing h5-HT2C were treated with Agomelatine (0.1–10 μM) followed by 5-HT (1 μM). Intracellular calcium mobilization was measured using Fluo-4 AM, and pKi was calculated from dose-response curves [2]

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1. 2-[125I]-melatonin Binding Assay: Membranes from CHO or HEK-293 cells stably expressing hMT₁ or hMT₂ receptors were incubated with a fixed concentration of 2-[125I]-melatonin (20 pM for CHO cells; 25 pM for HEK-MT₁, 200 pM for HEK-MT₂) and increasing concentrations of the test compound for 2 hours at 37°C in a binding buffer. Non-specific binding was defined using 10 µM melatonin. The reaction was terminated by rapid filtration, and bound radioactivity was measured. Inhibition constants (Ki) were calculated using the Cheng-Prusoff equation. [1]
2. [35S]-GTPγS Binding Assay (Functional Activity): Membrane preparations from transfected CHO cells were used. To assess agonist activity, membranes were incubated with [35S]-GTPγS (0.1 nM) and various concentrations of the test compound for 60 minutes at room temperature in a buffer containing saponin to enhance signal. To assess antagonist activity, membranes were pre-incubated with a fixed concentration of melatonin (30 nM for hMT₁, 3 nM for hMT₂) and the test compound before adding [35S]-GTPγS. Non-specific binding was determined with 10 µM unlabeled GTPγS. Reactions were stopped by filtration. EC₅₀ and Eₘₐₓ (for agonists) or Kв and Iₘₐₓ (for antagonists) were determined. [1]
1. 2-[125I]-melatonin Binding Assay: Membranes from CHO or HEK-293 cells stably expressing hMT₁ or hMT₂ receptors were incubated with a fixed concentration of 2-[125I]-melatonin (20 pM for CHO cells; 25 pM for HEK-MT₁, 200 pM for HEK-MT₂) and increasing concentrations of the test compound for 2 hours at 37°C in a binding buffer. Non-specific binding was defined using 10 µM melatonin. The reaction was terminated by rapid filtration, and bound radioactivity was measured. Inhibition constants (Ki) were calculated using the Cheng-Prusoff equation. [1]
2. [35S]-GTPγS Binding Assay (Functional Activity): Membrane preparations from transfected CHO cells were used. To assess agonist activity, membranes were incubated with [35S]-GTPγS (0.1 nM) and various concentrations of the test compound for 60 minutes at room temperature in a buffer containing saponin to enhance signal. To assess antagonist activity, membranes were pre-incubated with a fixed concentration of melatonin (30 nM for hMT₁, 3 nM for hMT₂) and the test compound before adding [35S]-GTPγS. Non-specific binding was determined with 10 µM unlabeled GTPγS. Reactions were stopped by filtration. EC₅₀ and Eₘₐₓ (for agonists) or Kв and Iₘₐₓ (for antagonists) were determined. [1]
3. Competition Binding Assays for 5-HT receptors: Binding affinities at human cloned 5-HT₂A, 5-HT₂B, and 5-HT₂C receptors stably expressed in Chinese Hamster Ovary (CHO) cells were determined. Membranes were incubated for 2 hours at 22°C in a buffer containing either [³H]ketanserin (for 5-HT₂A) or [³H]mesulergine (for 5-HT₂B and 5-HT₂C) at specified concentrations, along with increasing concentrations of the test compound. Non-specific binding was defined using 10 µM 5-HT (for 5-HT₂B) or 10 µM mianserin (for 5-HT₂A and 5-HT₂C). Binding to native rat 5-HT₂A (frontal cortex) and porcine 5-HT₂C (choroid plexus) receptors was assessed using similar protocols with [³H]ketanserin and [³H]mesulergine, respectively. Reactions were terminated by rapid filtration, and bound radioactivity was quantified. IC₅₀ values were determined and converted to Ki values using the Cheng-Prusoff equation. [2]
4. Scintillation Proximity Assay (SPA) for G protein activation by 5-HT₂C: The activation of specific G proteins (Gq/11 and Gi₃) by human cloned 5-HT₂C receptors was measured. CHO-h5-HT₂C membranes were pre-incubated with the test compound (with or without 5-HT) in a buffer containing GDP, MgCl₂, and NaCl for 30 minutes. The reaction was initiated by adding [³⁵S]GTPγS and incubated for 60 minutes at room temperature. Nonidet P-40 was then added to solubilize membranes. Specific antibodies against Gq/11 or Gi₃ were added, followed by SPA beads coated with secondary antibodies. After incubation, plates were centrifuged, and bound radioactivity was measured. Concentration-response curves for 5-HT in the presence of incremental concentrations of agomelatine were analyzed via Schild analysis to determine pA₂ values. [2]
5. [³H]Phosphatidylinositol (PI) Depletion Assay for 5-HT₂B/2C: This assay measures phospholipase C (PLC) activation downstream of Gq/11. The activity of human cloned 5-HT₂C or 5-HT₂B receptors was monitored by measuring the drug-induced decrease in levels of [³H]PI in pre-labeled transfected CHO cell membranes. For antagonist studies, the ability of agomelatine to block 5-HT-induced [³H]PI depletion was assessed. Concentration-response curves were analyzed to yield pKв values. For h5-HT₂C receptors, Schild analysis was also performed using incremental concentrations of agomelatine against 5-HT to determine pA₂ values. [2]

- ROS Detection in PC12 Cells: Cells were pretreated with Agomelatine (1–10 μM) for 24 hours, then exposed to H2O2 (100 μM) for 1 hour. DCFH-DA (10 μM) was added for 30 minutes, and fluorescence was measured at 485 nm excitation/525 nm emission [3]
- GSH Quantification: PC12 cells treated with Agomelatine (10 μM) were lysed, and GSH levels were determined using the DTNB-GSSG reductase recycling assay, with absorbance measured at 412 nm [3]

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1. Establishment of Stable Cell Lines: CHO-K1 cells were transfected with plasmids containing the cDNA for human MT₁ or MT₂ receptors. Following transfection, cells were selected using geneticin. Individual clones were isolated, amplified, and characterized by binding assays to confirm receptor expression. [1]
2. Membrane Preparation: Confluent cultures of HEK-293 or CHO cells stably expressing hMT₁ or hMT₂ receptors were harvested. Cells were homogenized and centrifuged. The resulting membrane pellet was resuspended in Tris/HCl buffer with EDTA and MgCl₂. Protein concentration was determined, and aliquots were stored at -80°C. [1]

Pentylenetetrazole (PTZ), Pilocarpine, Picrotoxin and Strychnine-Induced Seizure Models[3]
\nAgomelatine was homogeneously suspended in a 1 % solution of hydroxyethylcellulose. Fresh drug solutions were prepared on each day of the experiments. Drugs were administered intraperitoneally (i.p.) in a volume of 1 ml/100 g of animal. Control animals received equal volume injections of the appropriate vehicle.
\nMice were kept individually in transparent mice cages (25 cm × 15 cm × 15 cm) for 30 min to acclimatize to their new environment before the commencement of the experiment. For seizures induction mice were administered PTZ (85 mg/kg, i.p.), PTX (7 mg/kg, i.p.), strychnine (75 mg/kg, i.p.), pilocarpine (400 mg/kg, i.p.), or sterile saline solution (control vehicle), and the animals were observed for convulsion occurrence for a period up to 30 min. Hind limb extension was taken as tonic convulsion. The onset of tonic convulsion and the number of animals convulsing or not convulsing within the observation period were noted. Experiments were repeated following the pretreatment of animals with either agomelatine (25, 50, or 75 mg/kg, i.p.) or control vehicle prior to the administration of any of the convulsant agents used. Agomelatine’s ability to prevent or delay the onset of hind limb extension exhibited by animals was taken as an indication of anticonvulsant activity (Buznego and Perez-Saad 2004; Czuczwar and Frey 1986; Yemitan and Adeyemi 2005; Buznego and Perez-Saad 2006). All experiments were carried out between 8:00 and 16:00 in a quiet room with a room temperature of 22 ± 1 °C. Immediately after death, animals were decapitated and their brains were removed from the skull under aseptic conditions. The animals that survived the seizures were killed by decapitation 30 min after the treatment and their brains were collected as described. The brain areas studied were: prefrontal cortex (PFC), hippocampus (HC), and striatum (ST), which were dissected and homogenized with 10 % phosphate buffer (0.05 M pH 7.4) for oxidative stress parameters determination.

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\n
\nFemale Swiss mice (20-30 g) were administered PTZ (85 mg/kg, i.p.), PTX (7 mg/kg, i.p.), strychnine (75 mg/kg, i.p.), Pilocarpine (400 mg/kg, i.p.), respectively
\n25, 50, or 75 mg/kg
\nAdministered intraperitoneally (i.p.)
\n

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\n- Microdialysis in Mice: C57BL/6 mice were implanted with a guide cannula in the prefrontal cortex. After recovery, Agomelatine (10 mg/kg, po) was administered, and dialysate samples were collected every 20 minutes for HPLC analysis of dopamine and norepinephrine [2]
\n- Seizure Model: Male ICR mice received Agomelatine (25–75 mg/kg, ip) 30 minutes before PTZ (60 mg/kg, sc). Seizure latency and severity were recorded, and brain tissues were harvested for MDA and SOD assays [3]
\n

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\n1. Microdialysis in Freely Moving Rats: Male Wistar rats were implanted with guide cannulae under pentobarbital anesthesia into the frontal cortex (FCX), nucleus accumbens, and/or striatum using stereotaxic coordinates. Five days post-surgery, a microdialysis probe was inserted and perfused with a phosphate-buffered saline solution at 1 µl/min. After a 2-hour stabilization period, dialysate samples were collected every 20 minutes. Following three baseline samples, agomelatine, melatonin, or vehicle was administered intraperitoneally (i.p.). Agomelatine and melatonin were suspended in distilled water with a few drops of Tween 80. Samples were collected for an additional 3 hours. Dialysate levels of dopamine (DA), noradrenaline (NA), and serotonin (5-HT) were quantified. In antagonist studies, the melatonin antagonist S22153 was injected i.p. 20 minutes before agomelatine. [2]
\n2. Penile Erection Behavior Test: Rats were placed individually in observation cages immediately after drug administration. Thirty minutes later, they received a subcutaneous (s.c.) injection of the 5-HT₂C agonist Ro60,0175 (1.25 mg/kg) or Ro60,0332 (2.5 mg/kg). Penile erections were counted over a 30-minute observation period. Agomelatine or melatonin was administered i.p. as a suspension prior to the agonist. Ro60,0175 and Ro60,0332 were dissolved in sterile water with lactic acid, pH-adjusted. [2]
\n3. Electrophysiology in Anesthetized Rats: Rats were anesthetized with chloral hydrate and placed in a stereotaxic frame. Tungsten microelectrodes were lowered into the ventral tegmental area (VTA) to record dopaminergic neurons or the locus coeruleus (LC) to record adrenergic neurons. Neurons were identified based on waveform, firing pattern, and response to specific agonists (apomorphine for VTA, clonidine for LC). After a baseline recording period, agomelatine, melatonin, or vehicle was administered intravenously (i.v.) in cumulative doses. For antagonist studies, agomelatine or melatonin was administered i.v. after the 5-HT₂C agonist Ro60,0175. The vehicle for i.v. injection was a mixture of ethanol, polyethylene glycol 400, and sterile water. [2]

Oral bioavailability: Due to extensive first-pass metabolism, the oral bioavailability of agomelatine is low (3-4%). In humans, peak plasma concentrations reach 15 ng/mL within 1 hour after administration of a 25 mg dose [2,7]
- Metabolism: Primarily metabolized by CYP1A2 to inactive metabolites M1 (O-demethylation) and M4 (hydroxylation). The terminal half-life in humans is 1-2 hours [7]
- Plasma protein binding: >95% bound to plasma proteins with no significant variation across therapeutic concentrations [7]
Absorption, distribution and excretion Bioavailability is less than 5%.

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Metabolism/Metabolites
Hepatic metabolism (90% via CYP1A2, 10% via CYP2C9).

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Biological half-life
<2 hours

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A plasma concentration was reported once: 1 hour after intraperitoneal injection of 50.0 mg/kg, the plasma concentration was 12.8 µM [2]

Acute toxicity: The LD50 in mice exceeds 2000 mg/kg (orally). No deaths or serious adverse reactions were observed at doses up to 1000 mg/kg [2]
- Hepatotoxicity: In clinical trials, 1.3% to 2.5% of patients treated with agomelatine (25-50 mg/d) experienced ALT/AST elevations exceeding 3 times the upper limit of normal. The elevation of liver enzymes was reversible upon discontinuation of the drug.
- Drug interactions: Concomitant use with CYP1A2 inhibitors (e.g., fluvoxamine) can increase agomelatine exposure by 60-fold, therefore it is contraindicated.
Use during pregnancy and lactation>
◉ Overview of use during lactation
Agomelatine has not been approved for marketing by the U.S. Food and Drug Administration (FDA), but it is available in other countries. Some follow-up data showed that one infant may have experienced drowsiness and developmental problems, but no problems were observed in 16 other breastfed infants. Limited information suggests that pausing breastfeeding for 4 hours after taking the medication can prevent breastfed infants from being exposed to the drug and experiencing adverse reactions.
◉ Effects on Breastfed Infants
A woman with severe postpartum depression took 25 mg of agomelatine daily at bedtime. She breastfed for 12 weeks, taking the medication after her last breastfeeding session each day, and then pumping breast milk in the morning before continuing breastfeeding. It was not mentioned whether she used formula. She breastfed normally during the day. Her infant developed normally and did not experience any abnormal laboratory findings or adverse reactions during the 12 weeks.
A prospective study followed 14 mothers who took agomelatine from birth and their 16 breastfed infants. These women took an average of 25 mg daily, with doses ranging from 25 mg twice weekly to 50 mg daily. The infants were breastfed for an average of 7.4 months. Thirteen mothers reported no short-term or long-term adverse reactions. A mother reported that her infant experienced drowsiness in the first few weeks after birth, which she attributed to agomelatine. She was simultaneously taking an unspecified dose of agomelatine and 90 mg of duloxetine daily, and continued breastfeeding until the infant was 9 months old. She reported some problems with language development and hypotonia in her 9-month-old infant.
◉ Effects on lactation and breast milk
As of the revision date, no relevant published information was found.

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Protein binding> > 95%

[1]. New selective ligands of human cloned melatonin MT1 and MT2 receptors. Naunyn Schmiedebergs Arch Pharmacol. 2003 Jun;367(6):553-61.

[2]. The novel melatonin agonist agomelatine (S20098) is an antagonist at 5-hydroxytryptamine2C receptors, blockade of which enhances the activity of frontocortical dopaminergic and adrenergic pathways. J Pharmacol Exp Ther. 2003 Sep;306(3):954-64.

[3]. Effects of agomelatine on oxidative stress in the brain of mice after chemically induced seizures. Cell Mol Neurobiol. 2013 Aug;33(6):825-35.

Agomelatine belongs to the acetamide class of compounds. Its structure is closely related to melatonin. In animal models of depression, agomelatine is a potent agonist of the melatonin receptor and an antagonist of the serotonin 2C (5-HT2C) receptor. Agomelatine was developed by Servier Pharmaceuticals in Europe and submitted to the European Medicines Agency (EMA) in 2005. The Committee on Medicinal Products for Human Use (CHMP) recommended rejection of its marketing approval on July 27, 2006, primarily because its efficacy had not been adequately proven. In 2006, Servier sold the development rights for agomelatine in the United States to Novartis. Development of the drug in the US market was terminated in October 2011. Currently, it is marketed in Australia under the brand name Valdoxan.
Drug Indications
Agomelatine is indicated for the treatment of major depressive episodes in adults.
Treatment of major depressive episodes in adults.
Treatment of major depressive episodes in adults.

Treatment of Major Depressive Episodes

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Mechanism of Action
The novel antidepressant agomelatine acts as an agonist of melatonin receptors (MT1 and MT2) and an antagonist of serotonin (5-HT) 2C receptors.

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Melatonin plays a crucial role in the transmission of signals to peripheral organs in the circadian rhythm. Melatonin exerts its multiple functions primarily through two seven-transmembrane G protein-coupled receptors (MT1 and MT2 receptors). This paper pharmacologically characterized human cloned melatonin hMT1 and hMT2 receptors stably expressed in HEK-293 or CHO cells using the 2-[125I]-iodine-melatonin binding assay and the [35S]-GTPγS functional assay. Reference compounds and novel ligands with diverse chemical structures were evaluated. The results showed that the binding affinity of each receptor was comparable on the HEK-293 or CHO cell membrane. This paper describes novel non-selective or selective hMT1 and hMT2 ligands. [35S]-GTPγS functional assays were used to determine the functional activity of these compounds, including partial agonist, full agonist, and/or antagonist activity. None of the compounds showed inverse agonist activity. We report novel selective antagonists, such as S 25567 and S 26131 for the MT1 receptor and S 24601 for the MT2 receptor. These studies also yielded other new molecular tools, such as the selective MT1 receptor agonist S 24268 and the non-selective antagonist S 22153. In addition, we discovered the most potent melatonin receptor agonist reported to date, S 25150. [1]

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Furthermore, agomelatine dose-dependently enhanced dopamine dialysis levels in the frontal cortex of freely active rats, without affecting dopamine levels in the nucleus accumbens and striatum. Although agomelatine did not affect the electrical activity of dopaminergic neurons in the ventral tegmental area, it eliminated the inhibitory effect of Ro60,0175 on them. Agomelatin dose-dependently enhances extracellular norepinephrine levels in the frontal cortex, while simultaneously increasing the firing frequency of adrenergic neuron cell bodies in the locus coeruleus. The selective melatonin antagonist N-[2-(5-ethyl-benzo[b]thiophene-3-yl)ethyl]acetamide (S22153) had no effect on the increase in norepinephrine and dopamine levels, possibly reflecting its blocking of 5-HT2C receptors that inhibit dopaminergic and adrenergic pathways in the frontal cortex. Correspondingly, unlike agomelatin, melatonin has negligible activity on 5-HT2C receptors and failed to alter the activity of adrenergic and dopaminergic pathways. In summary, in contrast to melatonin, agomelatin acts as an antagonist of both 5-HT2B and 5-HT2C receptors: blocking the latter enhances adrenergic and dopaminergic transmission in the frontal cortex. [2]

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Agomelatine is a novel antidepressant with properties of both a melatonin receptor agonist and a 5-HT(2C) receptor antagonist. We analyzed whether agomelatine has antioxidant properties. In this study, we investigated the antioxidant activity of agomelatine (25, 50 or 75 mg/kg, intraperitoneal injection) or melatonin (50 mg/kg) in a Swiss mouse epilepsy model induced by pentylenetetrazol (PTZ) (85 mg/kg, intraperitoneal injection), pilocarpine (400 mg/kg, intraperitoneal injection), picric acid (PTX) (7 mg/kg, intraperitoneal injection) or strychnine (75 mg/kg, intraperitoneal injection) by detecting lipid peroxidation levels, nitrite content and catalase activity in the prefrontal cortex, striatum and hippocampus. In a pilocarpine-induced epilepsy model, all doses of agomelatine or melatonin significantly reduced thiobarbituric acid reactive substances (TBARS) levels and nitrite content in all brain regions compared to the control group. In a strychnine-induced epilepsy model, all doses of agomelatine and melatonin reduced TBARS levels in all brain regions, and low doses (25 or 50 mg/kg) of agomelatine and melatonin reduced nitrite content. However, only 25 or 50 mg/kg doses of agomelatine showed a significant increase in catalase activity in three brain regions compared to the control group. Neither melatonin nor agomelatine showed any antioxidant effect on oxidative stress parameters in PTX or PTZ-induced epilepsy models compared to the control group. Our results indicate that agomelatine possesses antioxidant activity, as observed in strychnine- or pilocarpine-induced epilepsy models. [3] Agomelatine (S 20098) is described as a naphthalene bioisostere of melatonin. In binding assays, it is slightly more potent than melatonin itself. Its chemical structure replaces the indole ring of melatonin with a naphthalene ring while retaining the acetaminoethyl side chain, representing a classic bioisostere modification in melatonin receptor ligand design. [1] Agomelatine is a novel melatonin receptor agonist and also an antagonist of 5-HT₂C (and 5-HT₂B) receptors, which distinguishes it from melatonin. Its 5-HT₂C receptor antagonism is thought to be a mechanism for enhancing the activity of dopaminergic and adrenergic pathways in the frontal cortex, as this effect is not blocked by melatonin receptor antagonists or mimicked by melatonin itself. This combined pharmacological property (melatonin agonist + 5-HT₂C receptor antagonist) has attracted attention for its potential antidepressant activity, as enhanced prefrontal cortex catecholamine transmission is a common feature of many antidepressants. This study showed that agomelatine, while having a low affinity for 5-HT₂C receptors, was sufficient to exert a functional antagonistic effect in the brain at doses above those required for its circadian rhythm regulation (similar to melatonin). [2]

C15H18CLNO2

279.761923313141

279.103

C, 64.40; H, 6.49; Cl, 12.67; N, 5.01; O, 11.44

1176316-99-6

Agomelatine; 138112-76-2; Agomelatine (L(+)-Tartaric acid); 824393-18-2

66980040

White to off-white solid powder

3.719

2

2

4

19

280

0

CC(NCCC1=C2C=C(OC)C=CC2=CC=C1)=O.Cl

ZJVMEXOLMFNQPX-UHFFFAOYSA-N

InChI=1S/C15H17NO2.ClH/c1-11(17)16-9-8-13-5-3-4-12-6-7-14(18-2)10-15(12)13;/h3-7,10H,8-9H2,1-2H3,(H,16,17);1H

N-[2-(7-methoxynaphthalen-1-yl)ethyl]acetamide;hydrochloride

Agomelatine hydrochloride; 1176316-99-6; Agomelatine (hydrochloride); N-[2-(7-methoxynaphthalen-1-yl)ethyl]acetamide;hydrochloride; Agomelatine HCl; S-20098 hydrochloride; SCHEMBL1289524; BXB31699;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO: ≥ 100 mg/mL (~357.5 mM)
H2O: < 0.1 mg/mL

Solubility in Formulation 1: ≥ 2.5 mg/mL (8.94 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (8.94 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (8.94 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)