Mode of action of agomelatine: synergy between melatonergic and 5-HT2C receptors

Implementation of a reference-scaled average bioequivalence approach for highly variable generic drug products of agomelatine in Chinese subjects

The aim of this study was to apply the reference-scaled average bioequivalence (RSABE) approach to evaluate the bioequivalence of 2 formulations of agomelatine, and to investigate the pharmacokinetic properties of agomelatine in Chinese healthy male subjects. This was performed in a single-dose, randomized-sequence, open-label, four-way crossover study with a one-day washout period between doses. Healthy Chinese males were randomly assigned to receive 25 mg of either the test or reference formulation. The formulations were considered bioequivalent if 90% confidence intervals (CIs) for the log-transformed ratios and ratio of geometric means (GMR) of AUC and C_max of agomelatine were within the predetermined bioequivalence range based on RSABE method. Results showed that both of the 90% CIs for the log-transformed ratios of AUC and C_max of 7-desmethyl-agomelatine and 3-hydroxy-agomelatine were within the predetermined bioequivalence range. The 90% CIs for natural log-transformed ratios of C_max, AUC_0–t and AUC_0–∞ of agomelatine (104.42–139.86, 101.33–123.83 and 97.90–117.94) were within the RSABE acceptance limits, and 3-hydroxy-agomelatine (105.55–123.03, 101.95–109.10 and 101.72–108.70) and 7-desmethyl-agomelatine (104.50–125.23, 102.36–111.50 and 101.62–110.64) were within the FDA bioequivalence definition intervals (0.80–1.25 for AUC and 0.75–1.33 for C_max). The RSABE approach was successful in evaluating the bioequivalence of these two formulations.

MT1 and MT2 Melatonin Receptors: A Therapeutic Perspective

Melatonin, or 5-methoxy-N-acetyltryptamine, is synthesized and released by the pineal gland and locally in the retina following a circadian rhythm, with low levels during the day and elevated levels at night. Melatonin activates two high-affinity G protein-coupled receptors, termed MT1 and MT2, to exert beneficial actions in sleep and circadian abnormality, mood disorders, learning and memory, neuroprotection, drug abuse, and cancer. Progress in understanding the role of melatonin receptors in the modulation of sleep and circadian rhythms has led to the discovery of a novel class of melatonin agonists for treating insomnia, circadian rhythms, mood disorders, and cancer. This review describes the pharmacological properties of a slow-release melatonin preparation (i.e., Circadin®) and synthetic ligands (i.e., agomelatine, ramelteon, tasimelteon), with emphasis on identifying specific therapeutic effects mediated through MT1 and MT2 receptor activation. Discovery of selective ligands targeting the MT1 or the MT2 melatonin receptors may promote the development of novel and more efficacious therapeutic agents.

Does melatonin treatment change emotional processing? Implications for understanding the antidepressant mechanism of agomelatine

The antidepressant, agomelatine, has a novel pharmacological profile, with agonist properties at M1 and M2 receptors and antagonist properties at 5HT2C receptors. Whether the antidepressant effects of this treatment are mediated by the drug's effects at the M1 and M2 receptors or the 5HT2C receptor or a synergy between these actions remains unclear. In the present study, a healthy volunteer model of emotional processing, which discriminates between effective and non-effective antidepressant compounds, was used to assess the contribution of melatonin agonism to the efficacy of agomelatine. Fifty-eight healthy volunteers were randomised to receive 7 days of once daily treatment with either 1 mg melatonin, 3 mg melatonin or placebo. Seven days treatment with 3 mg melatonin resulted in earlier bedtimes consistent with a phase advance in circadian rhythm. Some marginal effects of melatonin were observed on emotional processing; however, these were neither consistent with nor comparable to those seen following conventional antidepressant treatment or with agomelatine itself. These data suggest that the antidepressant action of agomelatine cannot be accounted for solely by its action at the M1 and M2 receptors.

Convergence of melatonin and serotonin (5-HT) signaling at MT2/5-HT2C receptor heteromers

Inasmuch as the neurohormone melatonin is synthetically derived from serotonin (5-HT), a close interrelationship between both has long been suspected. The present study reveals a hitherto unrecognized cross-talk mediated via physical association of melatonin MT2 and 5-HT2C receptors into functional heteromers. This is of particular interest in light of the "synergistic" melatonin agonist/5-HT2C antagonist profile of the novel antidepressant agomelatine. A suite of co-immunoprecipitation, bioluminescence resonance energy transfer, and pharmacological techniques was exploited to demonstrate formation of functional MT2 and 5-HT2C receptor heteromers both in transfected cells and in human cortex and hippocampus. MT2/5-HT2C heteromers amplified the 5-HT-mediated Gq/phospholipase C response and triggered melatonin-induced unidirectional transactivation of the 5-HT2C protomer of MT2/5-HT2C heteromers. Pharmacological studies revealed distinct functional properties for agomelatine, which shows "biased signaling." These observations demonstrate the existence of functionally unique MT2/5-HT2C heteromers and suggest that the antidepressant agomelatine has a distinctive profile at these sites potentially involved in its therapeutic effects on major depression and generalized anxiety disorder. Finally, MT2/5-HT2C heteromers provide a new strategy for the discovery of novel agents for the treatment of psychiatric disorders.

Mechanism of action of tasimelteon in non-24 sleep-wake syndrome: treatment for a circadian rhythm disorder in blind patients

Many individuals with total blindness can develop a circadian rhythm disorder-called non-24 sleep wake syndrome-because they cannot detect light to resynchronize their sleep-wake cycles. A new melatonin 1 and melatonin 2 agonist tasimelteon improves sleep in these patients, resetting their circadian sleep-wake clocks.

Agomelatine in the treatment of major depressive disorder: an assessment of benefits and risks

Agomelatine (AGM) was approved for the treatment of major depressive disorder (MDD) in adults by the European Medicines Agency (EMA) in February 2009. It is an analogue of melatonin and features a unique pharmacodynamic profile with agonism on both types of melatonergic receptors (MT1/MT2) and antagonism at serotonergic 5-HT2C receptors. There is, however, an ongoing debate regarding the efficacy and safety of this novel antidepressant agent, originally evoked by claims of a significant publication bias underlying the assessment of AGM being an effective antidepressant. Indeed, two recent comprehensive metaanalyses of published and unpublished clinical trials found evidence for a relevant publication bias. However, due to its statistically significant advantage over placebo based on the results of these metaanalyses AGM must be referred to as an effective antidepressant agent in the acute phase of MDD. However, the effect sizes of AGM in the treatment of MDD were evaluated as being small in comparison to other antidepressant agents. In addition, there is insufficient evidence for the efficacy of AGM in relapse prevention of MDD. Apart from efficacy issues, AGM appears to have the potential to exhibit severe hepatotoxicity (the EMA has identified AGM-associated “hepatotoxic reactions” as a new safety concern in September 2013) that is currently poorly understood. Considering these aspects, it seems inappropriate to evaluate AGM as an antidepressant agent of first choice. Nevertheless, its unique mechanism of action with particular sleep modulating effects may represent a specific treatment strategy for patients with particular characteristics; further studies with thorough characterization of patients are needed to test this hypothesis.

New insights on the antidepressant discontinuation syndrome

OBJECTIVE

Antidepressants are at best 50–55% effective. Non-compliance and the antidepressant discontinuation syndrome (ADS) are causally related yet poorly appreciated. While ADS is associated with most antidepressants, agomelatine seems to be devoid of such risk. We review the neurobiology and clinical consequences of antidepressant non-compliance and the ADS. Agomelatine is presented as a counterpoint to learn more on how ADS risk is determined by pharmacokinetics and pharmacology.

DESIGN

The relevant literature is reviewed through a MEDLINE search via PubMed, focusing on agomelatine and clinical and preclinical research on ADS.

RESULTS

Altered serotonergic dysfunction appears central to ADS so that how an antidepressant targets serotonin will determine its relative risk for inducing ADS and thereby affect later treatment outcome. Low ADS risk with agomelatine versus other antidepressants can be ascribed to its unique pharmacokinetic characteristics as well as its distinctive actions on serotonin, including melatonergic, monoaminergic and glutamatergic-nitrergic systems.

CONCLUSIONS

This review raises awareness of the long-term negative aspects of non-compliance and inappropriate antidepressant discontinuation, and suggests possible approaches to “design-out” a risk for ADS. It reveals intuitive and rational ideas for antidepressant drug design, and provides new thoughts on antidepressant pharmacology, ADS risk and how these affect long-term outcome.

Time-dependent activation of MAPK/Erk1/2 and Akt/GSK3 cascades: modulation by agomelatine

BACKGROUND

The novel antidepressant agomelatine, a melatonergic MT1/MT2 agonist combined with 5-HT2c serotonin antagonist properties, showed antidepressant action in preclinical and clinical studies. There is a general agreement that the therapeutic action of antidepressants needs the activation of slow-onset adaptations in downstream signalling pathways finally regulating neuroplasticity. In the last several years, particular attention was given to cAMP-responsive element binding protein (CREB)-related pathways, since it was shown that chronic antidepressants increase CREB phosphorylation and transcriptional activity, through the activation of calcium/calmodulin-dependent (CaM) and mitogen activated protein kinase cascades (MAPK/Erk1/2). Aim of this work was to analyse possible effects of chronic agomelatine on time-dependent changes of different intracellular signalling pathways in hippocampus and prefrontal/frontal cortex of male rats. To this end, measurements were performed 1 h or 16 h after the last agomelatine or vehicle injection.

RESULTS

We have found that in naïve rats chronic agomelatine, contrary to traditional antidepressants, did not increase CREB phosphorylation, but modulates the time-dependent regulation of MAPK/Erk1/2 and Akt/glycogen synthase kinase-3 (GSK-3) pathways.

CONCLUSION

Our results suggest that the intracellular molecular mechanisms modulated by chronic agomelatine may be partly different from those of traditional antidepressants and involve the time-dependent regulation of MAPK/Erk1/2 and Akt/GSK-3 signalling pathways. This could exert a role in the antidepressant efficacy of the drug.

Melatonergic drugs in development

Melatonin (N-acetyl-5-methoxytryptamine) is widely known as "the darkness hormone". It is a major chronobiological regulator involved in circadian phasing and sleep-wake cycle in humans. Numerous other functions, including cyto/neuroprotection, immune modulation, and energy metabolism have been ascribed to melatonin. A variety of studies have revealed a role for melatonin and its receptors in different pathophysiological conditions. However, the suitability of melatonin as a drug is limited because of its short half-life, poor oral bioavailability, and ubiquitous action. Due to the therapeutic potential of melatonin in a wide variety of clinical conditions, the development of new agents able to interact selectively with melatonin receptors has become an area of great interest during the last decade. Therefore, the field of melatonergic receptor agonists comprises a great number of structurally different chemical entities, which range from indolic to nonindolic compounds. Melatonergic agonists are suitable for sleep disturbances, neuropsychiatric disorders related to circadian dysphasing, and metabolic diseases associated with insulin resistance. The results of preclinical studies on animal models show that melatonin receptor agonists can be considered promising agents for the treatment of central nervous system-related pathologies. An overview of recent advances in the field of investigational melatonergic drugs will be presented in this review.

Melatonin pretreatment prevented the effect of dexamethasone negative alterations on behavior and hippocampal neurogenesis in the mouse brain

Glucocorticoids play various physiological functions via the glucocorticoid receptor (GR). Glucocorticoid is associated with the pathophysiology of depression. Dexamethasone (DEX), a synthetic GR agonist, has a greater affinity for GR than the mineralocorticoid receptor (MR) in the hippocampus of pigs and may mimic the effects of GR possession. DEX decreases neurogenesis and induces damage to hippocampal neurons that is associated with depressive-like behavior. Melatonin, a hormone mainly synthesized in the pineal gland, is a potent free radical scavenger and antioxidant. Melatonin alters noradrenergic transmission in depressed patients. It may be interesting to further explore the mechanism of melatonin that is associated with the role of stress as a key factor to precipitate depression and as a factor altering neurogenesis. In this study, we assessed the capability of melatonin to protect the hippocampus of mouse brains to counteract the effects of chronic DEX treatment for 21 days on depressive-like behavior and neurogenesis. Our results revealed that chronic administration of DEX induced depressive-like behavior and that this could be reversed by pretreatment with melatonin. Moreover, the number of 5-bromo-2-deoxyuridine (BrdU)-immunopositive cells and doublecortin (DCX; the neuronal-specific marker) protein levels were significantly reduced in the DEX-treated mice. Pretreatment with melatonin was found to renew BrdU and DCX expression in the dentate gyrus. Furthermore, pretreatment with melatonin prevented DEX-induced reductions in GR and an extracellular-signal-regulated kinase (ERK1/2) in the hippocampal area. Melatonin may protect hippocampal neurons from damage and reverse neurogenesis after chronic DEX by activating brain-derived neurotrophic (BDNF) and ERK1/2 cascades. These results revealed that melatonin pretreatment prevented the reduction of cell proliferation, immature neuron precursor cells, and GR and ERK1/2 expression. This finding indicates that melatonin attenuates the DEX-induced depressive-like behavior, supporting the notion that melatonin possesses anti-stress and neurogenic actions.

Agomelatine: mechanism of action and pharmacological profile in relation to antidepressant properties

Agomelatine behaves both as a potent agonist at melatonin MT1 and MT2 receptors and as a neutral antagonist at 5-HT2C receptors. Accumulating evidence in a broad range of experimental procedures supports the notion that the psychotropic effects of agomelatine are due to the synergy between its melatonergic and 5-hydroxytryptaminergic effects. The recent demonstration of the existence of heteromeric complexes of MT1 and MT2 with 5-HT2C receptors at the cellular level may explain how these two properties of agomelatine translate into a synergistic action that, for example, leads to increases in hippocampal proliferation, maturation and survival through modulation of multiple cellular pathways (increase in trophic factors, synaptic remodelling, glutamate signalling) and key targets (early genes, kinases). The present review focuses on the pharmacological properties of this novel antidepressant. Its mechanism of action, strikingly different from that of conventional classes of antidepressants, opens perspectives towards a better understanding of the physiopathological bases underlying depression.

On 'polypharmacy' and multi-target agents, complementary strategies for improving the treatment of depression: a comparative appraisal

Major depression is a heterogeneous disorder, both in terms of symptoms, ranging from anhedonia to cognitive impairment, and in terms of pathogenesis, with many interacting genetic, epigenetic, developmental and environmental causes. Accordingly, it seems unlikely that depressive states could be fully controlled by a drug possessing one discrete mechanism of action and, in the wake of disappointing results with several classes of highly selective agent, multi-modal treatment concepts are attracting attention. As concerns pharmacotherapy, there are essentially two core strategies. First, multi-target antidepressants that act via two or more complementary mechanisms and, second, polypharmacy, which refers to co-administration of two distinct drugs, usually in separate pills. Both multi-target agents and polypharmacy ideally couple a therapeutically unexploited action to a clinically established mechanism in order to enhance efficacy, moderate side-effects, accelerate onset of action and treat a broader range of symptoms. The melatonin MT1/MT2 agonist and 5-HT(2C) antagonist, agomelatine, which is effective in the short- and long-term treatment of depression, exemplifies the former approach, while evidence-based polypharmacy is illustrated by the adjunctive use of second-generation antipsychotics with serotonin reuptake inhibitors for treatment of resistant depression. Histone acetylation and methylation, ghrelin signalling, inflammatory modulators, metabotropic glutamate-7 receptors and trace amine-associated-1 receptors comprise attractive substrates for new multi-target and polypharmaceutical strategies. The present article outlines the rationale underpinning multi-modal approaches for treating depression, and critically compares and contrasts the pros and cons of established and potentially novel multi-target vs. polypharmaceutical treatments. On balance, the former appear the most promising for the elaboration, development and clinical implementation of innovative concepts for the more effective management of depression.

Subgroup analysis of the non-interventional study VIVALDI: agomelatine in treatment-naïve patients, in combination therapy and after treatment switch

OBJECTIVE

Agomelatine has demonstrated antidepressant efficacy in randomized, controlled trials. This non-interventional study VIVALDI evaluated agomelatine treatment under practice conditions.

METHODS

Psychiatrists documented the treatment of 3,317 patients over 12 weeks. According to the treatment condition three subgroups were selected: Agomelatine in treatment-naïve patients as mono-therapy (A), in pretreated patients as add-on-therapy (B), and in pretreated patients switched to agomelatine (C). Effect on depressive symptoms was evaluated via svMADRS and CGI. Daytime functioning and sleep-wake rhythm were assessed by a patient-questionnaire.

RESULTS

The svMADRS decreased from values > 30 at baseline to 12.8 (total population), 10.3 (A), 15.1 (B), and 13.5 (C). 76.1%, 55.7%, and 62.5% of patients were responders in subgroups A, B, and C, respectively, 65.8% in the total population. Remission was achieved in 66.5% (A), 44.7% (B), and 50.9% (C) of patients. After 12 weeks, subjective sleep quality and daytime functioning improved in the majority of patients. Adverse drug reactions (ADR/serious ADR) were reported for 6.0%/0% (A), 11.0%/0.2% (B), and 12.6%/0.3% (C) of patients. Overall, 25.8% of patients discontinued treatment prematurely, 5.2% due to ADR.

CONCLUSION

Agomelatine improved depressive symptoms, daytime functioning, and sleep-wake rhythm, and demonstrated good tolerability also in pretreated patients and combination therapy under routine practice.

Antidepressant efficacy of agomelatine: meta-analysis of published and unpublished studies

OBJECTIVE

To systematically review published and unpublished efficacy studies of agomelatine in people with depression.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Literature search (Pubmed, Embase, Medline), Cochrane Central Register of Controlled Trials, European Medicines Agency (EMA) regulatory file for agomelatine, manufacturers of agomelatine (Servier).

ELIGIBILITY CRITERIA

Double blind randomised placebo and comparator controlled trials of agomelatine in depression with standard depression rating scales.

DATA SYNTHESIS

Studies were pooled by using a random effects model with DerSimonian and Laird weights for comparisons with placebo and comparator antidepressant. The primary efficacy measure (change in rating scale score) was summarised with standardised mean difference (SMD; a measure of effect size) and secondary outcome measures with relative risks. All results were presented with 95% confidence intervals. Statistical heterogeneity was explored by visual inspection of funnel plots and by the I(2) statistic. Moderators of effect were explored by meta-regression.

RESULTS

We identified 20 trials with 7460 participants meeting inclusion criteria (11 in the published literature, four from the European Medicines Agency file, and five from the manufacturer). Almost all studies used the 17 item Hamilton depression rating scale (score 0-50). Agomelatine was significantly more effective than placebo with an effect size (SMD) of 0.24 (95% confidence interval 0.12 to 0.35) and relative risk of response 1.25 (1.11 to 1.4). Compared with other antidepressants, agomelatine showed equal efficacy (SMD 0.00, -0.09 to 0.10). Significant heterogeneity was uncovered in most analyses, though risk of bias was low. Published studies were more likely than unpublished studies to have results that suggested advantages for agomelatine.

CONCLUSIONS

Agomelatine is an effective antidepressant with similar efficacy to standard antidepressants. Published trials generally had more favourable results than unpublished studies.

Agomelatine in the tree shrew model of depression: effects on stress-induced nocturnal hyperthermia and hormonal status

The antidepressive drug agomelatine combines the properties of an agonist of melatonergic receptors 1 and 2 with an antagonist of the 5-HT2C receptor. We analyzed the effects of agomelatine in psychosocially stressed male tree shrews, an established preclinical model of depression. Tree shrews experienced daily social stress for a period of 5 weeks and were concomitantly treated with different drugs daily for 4 weeks. The effects of agomelatine (40 mg/kg/day) were compared with those of the agonist melatonin (40 mg/kg/day), the inverse 5-HT2C antagonist S32006 (10mg/kg/day), and the SSRI fluoxetine (15 mg/kg/day). Nocturnal core body temperature (CBT) was recorded by telemetry, and urinary norepinephrine and cortisol concentrations were measured. Chronic social stress induced nocturnal hyperthermia. Agomelatine normalized the CBT in the fourth week of the treatment (T4), whereas the other drugs did not significantly counteract the stress-induced hyperthermia. Agomelatine also reversed the stress-induced reduction in locomotor activity. Norepinephrine concentration was elevated by the stress indicating sympathetic hyperactivity, and was normalized in the stressed animals treated with agomelatine or fluoxetine but not in those treated with melatonin or S32006. Cortisol concentration was elevated by stress but returned to basal levels by T4 in all animals, irrespective of the treatment. These observations show that agomelatine has positive effects to counteract stress-induced physiological processes and to restore the normal rhythm of nocturnal CBT. The data underpin the antidepressant properties of agomelatine and are consistent with a distinctive profile compared to its constituent pharmacological components and other conventional agents.

Synthetic melatoninergic ligands: achievements and prospects

Pineal hormone melatonin is widely used in the treatment of disorders of circadian rhythms. The presence of melatonin receptors in various animal tissues motivates the use of this hormone in some other diseases. For this reason, in recent years investigators continued the search for synthetic analogues of melatonin which are metabolically stable and selective to receptors. This review includes recent information about the most famous melatonin analogues, their structure, properties, and physiological features of the interaction with melatonin receptors.

Role of melatonin, serotonin 2B, and serotonin 2C receptors in modulating the firing activity of rat dopamine neurons

Melatonin has been widely used for the management of insomnia, but is devoid of antidepressant effect in the clinic. In contrast, agomelatine which is a potent melatonin receptor agonist is an effective antidepressant. It is, however, a potent serotonin 2B (5-HT(2B)) and serotonin 2C (5-HT(2C)) receptor antagonist as well. The present study was aimed at investigating the in vivo effects of repeated administration of melatonin (40 mg/kg/day), the 5-HT(2C) receptor antagonist SB 242084 (0.5 mg/kg/day), the selective 5-HT(2B) receptor antagonist LY 266097 (0.6 mg/kg/day) and their combination on ventral tegmental area (VTA) dopamine (DA), locus coeruleus (LC) norepinephrine (NE), and dorsal raphe nucleus (DRN) serotonin (5-HT) firing activity. Administration of melatonin twice daily increased the number of spontaneously active DA neurons but left the firing of NE neurons unaltered. Long-term administration of melatonin and SB 242084, by themselves, had no effect on the firing rate and burst parameters of 5-HT and DA neurons. Their combination, however, enhanced only the number of spontaneously active DA neurons, while leaving the firing of 5-HT neurons unchanged. The addition of LY 266097, which by itself is devoid of effect, to the previous regimen increased for DA neurons the number of bursts per minute and the percentage of spikes occurring in bursts. In conclusion, the combination of melatonin receptor activation as well as 5-HT(2C) receptor blockade resulted in a disinhibition of DA neurons. When 5-HT(2B) receptors were also blocked, the firing and the bursting activity of DA neurons were both enhanced, thus reproducing the effect of agomelatine.

Is there a role for agomelatine in the treatment of anxiety disorders?A review of published data

Anxiety disorders (Ads) are the most common type of psychiatric disorders, Pharmacologic options studied for treating ADs may include benzodiazepines, tricyclic antidepressants (TCA), selective serotonin reuptake inhibitors (SSRIs), noradrenergic and specific serotonergic antidepressants (NaSSA) and serotonin and noradrenaline reuptake inhibitors (SNRIs). Agomelatine, a new melatonergic antidepressant, has been shown effective in various types of mood disorders. Moreover, some evidence points towards a possible efficacy of such a drug in the treatment of ADs. Therefore, the aim of this review was to elucidate current (facts and views) data on the role of agomelatine in the treatment of ADs. The trials evaluating agomelatine in the treatment of generalized anxiety disorder are few but, overall, encouraging in regards to its efficacy. However, further randomized, placebo-controlled studies on larger samples use are needed. Apart from some interesting case reports, no large studies are, to date, present in literature regarding agomelatine in the treatment of other ADs, such as panic disorder, social anxiety disorder, obsessive-compulsive disorder and post-traumatic stress disorder. Therefore, the clinical efficacy and the relative good tolerability of agomelatine in generalized anxiety (GAD) warrants further investigation in ADs.

Modulation of the inflammatory response in rats chronically treated with the antidepressant agomelatine

Growing evidence suggests that the activation of the inflammatory/immune system contributes to depression pathogenesis, a hypothesis that might hold strong clinical implication. Indeed more than 30% of depressed patients fail to achieve remission, which poses the necessity to identify systems that may represent novel targets for medications. Accordingly, goal of this study was to evaluate the ability of the antidepressant agomelatine to modulate specific components of the immune response in the rat brain following an inflammatory challenge with lipopolysaccharide (LPS). To this aim, adult male rats were chronically treated with agomelatine before being acutely challenged with LPS 16 h after the last drug administration. Rats were sacrificed 2, 6, or 24h after the challenge and several components of the inflammatory response have been investigated by using real-time PCR or ELISA. We found that agomelatine significantly reduced the LPS-induced up-regulation of the pro-inflammatory cytokines interleukin-1β and interleukin-6 in the rat brain as well as at peripheral level. At central level, these effects are associated to the inhibition of NF-κB translocation as well as to alterations of mechanisms responsible for microglia activation. In addition, we found that agomelatine was also able to alter the expression of enzymes related to the kynurenine pathway that are thought to represent important mediators to inflammation-related depression. These data disclose novel properties that may contribute to the therapeutic effect of agomelatine providing evidence for a crucial role of specific components of the immune/inflammatory system in the antidepressant response and thereby in depression etiopathology.

A naturalistic evaluation and audit database of agomelatine: clinical outcome at 12 weeks

OBJECTIVE

To determine the effectiveness of agomelatine in routine clinical practice and explore factors associated with response and continuation.

METHOD

Consecutive patients prescribed agomelatine in participating psychiatric services were included. Patient demographic and outcome data were collected at treatment initiation and then at weeks 4, 8 and 12. Outcomes were analysed with respect to clinical and demographic factors.

RESULTS

A total of 110 patients from nine NHS trusts were followed through 12 weeks of treatment. Agomelatine was largely used in difficult-to-treat or refractory patients: 83 (75%) had failed to respond to, or relapsed on, prior antidepressants. There were high rates of physical (54.5%) and psychiatric (50.0%) comorbidity. At 12 weeks of treatment, 68 (62%) continued agomelatine treatment. Overall, 69 subjects (62.7%) improved by at least one point of the Clinical Global Impression (severity) scale. Of 42 who discontinued, 23 (56%) discontinued because of lack of efficacy and 10 (24%) due to an adverse event. Of all variables examined, only a history of more than five episodes of depression significantly predicted discontinuation of treatment (OR continuation - 0.36, 95% CI 0.14, 0.95).

CONCLUSION

Agomelatine was effective and generally well tolerated in a cohort of difficult-to-treat patients in clinical practice.

Chronic treatment with agomelatine or venlafaxine reduces depolarization-evoked glutamate release from hippocampal synaptosomes

BACKGROUND

Growing compelling evidence from clinical and preclinical studies has demonstrated the primary role of alterations of glutamatergic transmission in cortical and limbic areas in the pathophysiology of mood disorders. Chronic antidepressants have been shown to dampen endogenous glutamate release from rat hippocampal synaptic terminals and to prevent the marked increase of glutamate overflow induced by acute behavioral stress in frontal/prefrontal cortex. Agomelatine, a new antidepressant endowed with MT1/MT2 agonist and 5-HT2C serotonergic antagonist properties, has shown efficacy at both preclinical and clinical levels.

RESULTS

Chronic treatment with agomelatine, or with the reference drug venlafaxine, induced a marked decrease of depolarization-evoked endogenous glutamate release from purified hippocampal synaptic terminals in superfusion. No changes were observed in GABA release. This effect was accompanied by reduced accumulation of SNARE protein complexes, the key molecular effector of vesicle docking, priming and fusion at presynaptic membranes.

CONCLUSIONS

Our data suggest that the novel antidepressant agomelatine share with other classes of antidepressants the ability to modulate glutamatergic transmission in hippocampus. Its action seems to be mediated by molecular mechanisms located on the presynaptic membrane and related with the size of the vesicle pool ready for release.

Successful Treatment with Agomelatine in NES: A Series of Five Cases

The NES is an emerging disease in eating behavior that combines eating disorders, sleep, mood and stress. In recent years, the NES is becoming more interested in close association with obesity and depression.

In the present study we have followed for 12 weeks 5 patients (2 males and 3 females) with NES and comorbid depression treated with agomelatine (25 mg / day for the first two weeks, then 50 mg / day), an antidepressant similar of melatonin.

At the end of the three months of treatment, it was found an improvement in symptoms characteristic of the NES, as assessed by a reduction an average of the NEQ (from 31 to 22.8), improved mood, mean values ​​reduced by 23, 2 to 13.2 on the HAM-D, weight reduction, an average of 3.6 kg reduction in average weekly awakenings from 12 to 6.4 and the time of snoring and motion detected polysomnography. The serum chemistry values ​​remained stable and there were no reported adverse events.

The present study showed that the treatment with agomelatine has improved the symptoms of NES and mood, decrease of body weight, reduce, albeit not in an optimal manner, the number of awakenings per night with a reduction of movement time and snoring . Of course, these preliminary data need to be confirmed by controlled trials on a larger sample.

Melatonin potentiates running wheel-induced neurogenesis in the dentate gyrus of adult C3H/HeN mice hippocampus

This study assessed the role of melatonin in modulating running wheel(RW)-induced hippocampal neurogenesis in adult C3H/HeN mice. Chronic melatonin (0.02 mg/mL, oral for 12 days) treatment did not affect cell proliferation or cell survival determined by the number of BrdU-positive cells in dentate gyrus of mice with access to fixed wheel (FW). RW activity significantly increased cell proliferation [RW (n = 8) versus FW (n = 6): dorsal, 199 ± 18 versus 125 ± 12, P < 0.01; ventral, 211 ± 15 versus 123 ± 13, P < 0.01] and newborn cell survival [RW (n = 7) versus FW (n = 8): dorsal, 45 ± 8.5 versus 15 ± 1.8, P < 0.01; ventral, 48 ± 8.1 versus 15 ± 1.4)] in the dorsal and ventral dentate gyrus. Oral melatonin treatment further potentiated RW activity-induced cell survival in both areas of the dentate gyrus [melatonin (n = 10) versus vehicle (n = 7): dorsal, 63 ± 5.4 versus 45 ± 8.5 P < 0.05; ventral, 75 ± 7.9 versus 48 ± 8.1, P < 0.01] and neurogenesis [melatonin (n = 8) versus vehicle (n = 8): dorsal, 46 ± 3.4, versus 34 ± 4.5, P < 0.05; ventral, 41 ± 3.4 versus 25 ± 2.4, P < 0.01]. We conclude that melatonin potentiates RW-induced hippocampal neurogenesis by enhancing neuronal survival suggesting that the combination of physical exercise and melatonin may be an effective treatment for diseases affecting the hippocampus neurogenesis.

Agomelatine and sertraline for the treatment of depression in type 2 diabetes mellitus

OBJECTIVE

The present study compared the efficacy of agomelatine and sertraline in the treatment of symptoms of depression/anxiety, diabetes self-care and metabolic control in a sample of depressed patients with non-optimally controlled type 2 diabetes mellitus (DM).

METHOD

This was an observational open label study of 40 depressed patients with DM who were randomly assigned to receive either agomelatine or sertraline, and were assessed over a 4-month period for depression, anxiety, self-care, fasting plasma glucose, haemoglobin A1c and body weight.

RESULTS

Lower anxiety and depression scores as well as higher self-care scores were measured in the agomelatine group compared with the sertraline group after 4 months of treatment. Although the main effects of treatment on final body weight and fasting plasma glucose were not significant, significantly lower final haemoglobin A1c levels were measured in the agomelatine group compared with the sertraline group. Both antidepressants were well tolerated and none of the patients dropped-out of the study.

CONCLUSION

The main finding of the present small pilot study was that agomelatine may be a promising agent in the treatment of symptoms of depression and anxiety as well as in the improvement of health-related behaviours, in depressed patients with type 2 DM possibly offering some advantages over sertraline. However, the lack of a placebo control group limits the generalisability of the findings and warrants further studies.

Electrophysiological effects of repeated administration of agomelatine on the dopamine, norepinephrine, and serotonin systems in the rat brain

Agomelatine is a melatonergic MT1/MT2 agonist and a serotonin (5-HT) 5-HT(2C) antagonist. The effects of 2-day and 14-day administration of agomelatine were investigated on the activity of ventral tegmental area (VTA) dopamine (DA), locus coeruleus (LC) norepinephrine (NE), and dorsal raphe nucleus (DRN) 5-HT neurons using in vivo electrophysiology in rats. The 5-HT(1A) transmission was assessed at hippocampus CA3 pyramidal neurons. After a 2-day regimen of agomelatine (40 mg/kg/day, i.p.), an increase in the number of spontaneously active VTA-DA neurons (p<0.001) and in the firing rate of LC-NE neurons (p<0.001) was observed. After 14 days, the administration of agomelatine induced an increase in: (1) the number of spontaneously active DA neurons (p<0.05), (2) the bursting activity of DA neurons (bursts/min, p<0.01 and percentage of spikes occurring in bursts, p<0.05), (3) the firing rate of DRN-5-HT neurons (p<0.05), and (4) the tonic activation of postsynaptic 5-HT(1A) receptors located in the hippocampus. The increase in 5-HT firing rate was D2 dependent, as it was antagonized by the D2 receptor antagonist paliperidone. The enhancement of NE firing was restored by the 5-HT(2A) receptor antagonist MDL-100,907 after the 14-day regimen. All the effects of agomelatine were antagonized by a single administration of the melatonergic antagonist S22153 (except for the increase in the percentage of spikes occurring in burst for DA neurons). The present results suggest that (1) agomelatine exerts direct (2 days) and indirect (14 days) modulations of monoaminergic neuronal activity and (2) the melatonergic agonistic activity of agomelatine contributes to the enhancement of DA and 5-HT neurotransmission.

Agomelatine as monotherapy for major depression: an outpatient, open-label study

BACKGROUND

Agomelatine is a novel antidepressant agonist to MT1 and MT2 subtypes of melatoninergic receptors (MT1 and MT2) and antagonist to 5-HT2C subtype of serotonergic (5-HT2C) receptors, which has shown antidepressant efficacy in short-term and long-term trials as well as in clinical practice. The purpose of this study was to assess the antidepressant efficacy, safety, and the influence of agomelatine on the functioning of patient in common clinical practice.

METHODS

In this open-label, 8-week, multicenter, Phase IV trial, 111 patients with mainly moderate to severe major depressive disorder (39% treatment-naïve) were treated with agomelatine 25-50 mg/day for up to 8 weeks. The primary endpoint was the mean change in total Montgomery and Åsberg Depression Rating Scale (MADRS). Secondary endpoints included assessment of clinical response (defined as a reduction in total MADRS score of ≥50%), and change in Clinical Global Impression scales, Global Assessment of Functioning scale, Sheehan Disability Scale, and CircScreen sleep questionnaire scores. Safety and tolerability were also monitored.

RESULTS

Of the 111 patients enrolled, 94 completed the study. The total MADRS score significantly decreased by the first week of treatment and continued to decline significantly until study completion, with an estimated mean change of 3.9 ± 3.9 and 17.2 ± 8.0 at the first and eighth week of the study (last observation carried forward analyses). All other secondary endpoints significantly improved from early treatment evaluation to study completion. A clinical response was observed in 14.1% of patients after the first week, rising to 74.5% of patients at study completion. There were 31 spontaneously reported adverse events in 17 patients, and most were mild to moderate in severity.

CONCLUSION

This study showed good short-term efficacy for agomelatine in outpatients with major depressive episodes. Treatment with agomelatine achieved early and consistent responses for symptoms of depression and other dimensions of clinical and functional status. Agomelatine achieved significant improvements in daily functioning of patients, and had good tolerability. Clinically, no hepatic events were observed.

Adjunctive agomelatine therapy in the treatment of acute bipolar II depression: a preliminary open label study

PURPOSE

The circadian rhythm hypothesis of bipolar disorder (BD) suggests a role for melatonin in regulating mood, thus extending the interest toward the melatonergic antidepressant agomelatine as well as type I (acute) or II cases of bipolar depression.

PATIENTS AND METHODS

Twenty-eight depressed BD-II patients received open label agomelatine (25 mg/bedtime) for 6 consecutive weeks as an adjunct to treatment with lithium or valproate, followed by an optional treatment extension of 30 weeks. Measures included the Hamilton depression scale, Pittsburgh Sleep Quality Index, the Clinical Global Impression Scale-Bipolar Version, Young Mania Rating Scale, and body mass index.

RESULTS

Intent to treat analysis results demonstrated that 18 of the 28 subjects (64%) showed medication response after 6 weeks (primary study endpoint), while 24 of the 28 subjects (86%) responded by 36 weeks. When examining primary mood stabilizer treatment, 12 of the 17 (70.6%) valproate and six of the 11 (54.5%) lithium patients responded by the first endpoint. At 36 weeks, 14 valproate treated (82.4%) and 10 lithium treated (90.9%) subjects responded. At 36 weeks, there was a slight yet statistically significant (P = 0.001) reduction in body mass index and Pittsburgh Sleep Quality Index scores compared to respective baseline values, regardless of mood stabilizer/outcome. Treatment related drop-out cases included four patients (14.28%) at week 6 two valproate-treated subjects with pseudo-vertigo and drug-induced hypomania, respectively, and two lithium-treated subjects with insomnia and mania, respectively. Week 36 drop outs were two hypomanic cases, one per group.

CONCLUSION

Agomelatine 25 mg/day was an effective and well-tolerated adjunct to valproate/lithium for acute depression in BD-II, suggesting the need for confirmation by future double blind, controlled clinical trials.

The neurobiology of depression and antidepressant action

We present a comprehensive overview of the neurobiology of unipolar major depression and antidepressant drug action, integrating data from affective neuroscience, neuro- and psychopharmacology, neuroendocrinology, neuroanatomy, and molecular biology. We suggest that the problem of depression comprises three sub-problems: first episodes in people with low vulnerability ('simple' depressions), which are strongly stress-dependent; an increase in vulnerability and autonomy from stress that develops over episodes of depression (kindling); and factors that confer vulnerability to a first episode (a depressive diathesis). We describe key processes in the onset of a 'simple' depression and show that kindling and depressive diatheses reproduce many of the neurobiological features of depression. We also review the neurobiological mechanisms of antidepressant drug action, and show that resistance to antidepressant treatment is associated with genetic and other factors that are largely similar to those implicated in vulnerability to depression. We discuss the implications of these conclusions for the understanding and treatment of depression, and make some strategic recommendations for future research.

Agomelatine: Its Role in the Management of Major Depressive Disorder

Circadian rhythm abnormalities, as shown by sleep/wake cycle disturbances, constitute one the most prevalent signs of depressive illness; advances or delays in the circadian phase are documented in patients with major depressive disorder (MDD), bipolar disorder, and seasonal affective disorder (SAD). The disturbances in the amplitude and phase of rhythm in melatonin secretion that occur in patients with depression resemble those seen in chronobiological disorders, thus suggesting a link between disturbed melatonin secretion and depressed mood. Based on this, agomelatine, the first MT1/MT2 melatonergic agonist displaying also 5-HT2C serotonergic antagonism, has been introduced as an antidepressant. Agomelatine has been shown to be effective in several animal models of depression and anxiety and it has beneficial effects in patients with MDD, bipolar disorder, or SAD. Among agomelatine's characteristics are a rapid onset of action and a pronounced effectiveness for correcting circadian rhythm abnormalities and improving the sleep/wake cycle. Agomelatine also improves the 3 functional dimensions of depression—emotional, cognitive, and social—thus aiding in the full recovery of patients to a normal life.

Neuroimmunomodulation in unipolar depression: a focus on chronobiology and chronotherapeutics

The rising burden of unipolar depression along with its often related sleep disturbances, as well as increasing rates of sleep restriction in modern society, make the search for an extended understanding of the aetiology and pathophysiology of depression necessary. Accumulating evidence suggests an important role for the immune system in mediating disrupted neurobiological and chronobiological processes in depression. This review aims to provide an overview of the neuroimmunomodulatory processes involved with depression and antidepressant treatments with a special focus on chronobiology, chronotherapeutics and the emerging field of immune-circadian bi-directional crosstalk. Increasing evidence suggests that chronobiological disruption can mediate immune changes in depression, and likewise, immune processes can mediate chronobiological disruption. This may suggest a bi-directional relationship in immune-circadian crosstalk. Furthermore, given the immunomodulatory effects of antidepressants and chronotherapeutics, as well as their associated beneficial effects on circadian disturbance, we--and others--suggest that these therapeutic agents may exert their chronobiotic effects partially via the neuroimmune system. Further research is required to better elucidate the mechanisms of immune involvement in the chronobiology of depression.

Anhedonia and major depression: the role of agomelatine

Anhedonia is a condition in which the capacity to experience pleasure is totally or partially lost. Although anhedonia is a feature of major depressive disorder according to DSM IV criteria for major depression diagnosis, so far it has received relatively little attention. The scale that is most commonly used in the measurement of anhedonia is the Snaith-Hamilton Pleasure Scale (SHAPS), a brief 14-item self-report questionnaire designed to measure hedonic tone and its absence. Two studies have described the efficacy of agomelatine in the treatment of anhedonia: an open-label study and a comparative trial versus the antidepressant venlafaxine XR. In both studies agomelatine significantly reduced anhedonia, as indicated using the SHAPS. This reduction was observed after the first week of treatment (P<0.05) and at different times until the end of the trial. Moreover, in the comparative trial, a significant difference between groups was observed in favor of agomelatine, after 1 (P<0.05), 2 (P<0.01), and 8 weeks (P<0.01). The possible effect of agomelatine on anhedonia may represent a novel area of interest among antidepressant agents and deserves further investigation, with larger samples and double-blind placebo-controlled designs.

Synergistic mechanisms involved in the antidepressant effects of agomelatine

Agomelatine is a novel and clinically effective antidepressant drug with melatonergic (MT1/MT2) agonist and 5-HT(2C) receptor antagonist properties. Both receptorial components are widely expressed in the central nervous system and it seems that this compound could act synergistically on both the melatonergic and the 5-HT(2C) receptors. In this review we will briefly summarize the preclinical evidence suggesting that the molecular-cellular effects of agomelatine and in turn its antidepressant activity are the result of a synergistic action between its agonism at MT1/MT2 and antagonism at 5-HT(2C) receptors. The antidepressant properties of agomelatine related to its effect on neurogenesis, cell survival, brain-derived neurotrophic factor (BDNF), activity-regulated cytoskeleton associated protein (Arc) and stress-induced glutamate release, appear to be due to this synergistic action. Compared with traditional antidepressants which also affect these parameters, agomelatine is the only one able to resynchronize these effectors at distinct levels, circuital and intracellular. This suggests that agomelatine effects in restoring circadian rhythms and relieving depressive symptoms result from a synergistic interaction between melatonergic and serotonergic receptors.