Agomelatine: efficacy at each phase of antidepressant treatment

Agomelatine: An astounding sui-generis antidepressant?

Major depressive disorder (MDD) is one of the foremost causes of disability and premature death worldwide. Although the available antidepressants are effective and well tolerated, they also have many limitations. Therapeutic advances in developing a new drug's ultimate relation between MDD and chronobiology, which targets the circadian rhythm, have led to a renewed focus on psychiatric disorders. In order to provide a critical analysis about antidepressant properties of agomelatine, a detailed PubMed (Medline), Scopus (Embase), Web of Science (Web of Knowledge), Cochrane Library, Google Scholar, and PsycInfo search was performed using the following keywords: melatonin analog, agomelatine, safety, efficacy, adverse effects, pharmacokinetics, pharmacodynamics, circadian rhythm, sleep disorders, neuroplasticity, MDD, bipolar disorder, anhedonia, anxiety, generalized anxiety disorder (GAD), and mood disorders. Agomelatine is a unique melatonin analog with antidepressant properties and a large therapeutic index that improves clinical safety. It is a melatonin receptor agonist (MT1 and MT2) and a 5-HT2C receptor antagonist. The effects on melatonin receptors enable the resynchronization of irregular circadian rhythms with beneficial effects on sleep architectures. In this way, agomelatine is accredited for its unique mode of action, which helps to exert antidepressant effects and resynchronize the sleep-wake cycle. To sum up, an agomelatine has not only antidepressant properties but also has anxiolytic effects.

Agomelatine, A Potential Multi-Target Treatment Alternative for Insomnia, Depression, and Osteoporosis in Postmenopausal Women: A Hypothetical Model

Insomnia, which is associated with menopausal depression, is a common symptom of menopause. Both symptoms have a common etiology, and can affect each other significantly. Pharmacological interventions, including hypnotics and antidepressants, and non-pharmacological therapies are generally administered in clinical practice for insomnia treatment. As another menopausal disorder, osteoporosis is described as a disease of low bone mineral density (BMD), affecting nearly 200 million women worldwide. Postmenopausal osteoporosis is common among middle-aged women. Since postmenopausal osteoporosis mainly results from low estrogen levels, menopausal hormone therapy (HT) is considered the first-line option for the prevention of osteoporosis during the menopausal period. However, almost no study has evaluated novel treatments for the combined prevention of insomnia, depression, and osteoporosis. Hence, it is necessary to develop new multi-target strategies for the treatment of these disorders to improve the quality of life during this vulnerable period. Melatonin is the major regulator of sleep, and it has been suggested to be safe and effective for bone loss therapy by MT-2 receptor activity. As a result, we hypothesize that agomelatine, an MT-1 and MT-2 receptor agonist and 5-HT_2C receptor antagonist, holds promise in the combined treatment of insomnia, depression, and osteoporosis in middle-aged women during menopause.

Physicochemical Characterization and Pharmacokinetics of Agomelatine-Loaded PLGA Microspheres for Intramuscular Injection

PURPOSE

The aim of this study was to design agomelatine loaded long acting injectable microspheres, with an eventual goal of reducing the frequency of administration and improving patient compliance in treatment of depression.

METHODS

AGM-loaded microspheres were prepared by an O/W emulsion solvent evaporation method. The physicochemical properties and in vitro performance of the microspheres were characterized. The pharmacokinetics of different formulations with various particle sizes and drug loadings were evaluated.

RESULTS

AGM-loaded microspheres with drug loading of 23.7% and particle size of 60.2 μm were obtained. The in vitro release profiles showed a small initial burst release (7.36%) followed by a fast release, a period of lag time and a second accelerated release. Pore formation and pore closure were observed in vitro, indicating that the release of drug from microspheres is dominated by water-filled pores. Pharmacokinetic studies showed that AGM microspheres could release up to 30 days in vivo at a steady plasma concentration. As well, particle size and drug loading could significantly influence the in vivo release of AGM microspheres.

CONCLUSIONS

AGM-loaded microspheres are a promising carrier for the treatment of major depressant disorder.

Depressive disorders: Processes leading to neurogeneration and potential novel treatments

Mood disorders are wide spread with estimates that one in seven of the population are affected at some time in their life (Kessler et al., 2012). Many of those affected with severe depressive disorders have cognitive deficits which may progress to frank neurodegeneration. There are several peripheral markers shown by patients who have cognitive deficits that could represent causative factors and could potentially serve as guides to the prevention or even treatment of neurodegeneration. Circadian rhythm misalignment, immune dysfunction and oxidative stress are key pathologic processes implicated in neurodegeneration and cognitive dysfunction in depressive disorders. Novel treatments targeting these pathways may therefore potentially improve patient outcomes whereby the primary mechanism of action is outside of the monoaminergic system. Moreover, targeting immune dysfunction, oxidative stress and circadian rhythm misalignment (rather than primarily the monoaminergic system) may hold promise for truly disease modifying treatments that may prevent neurodegeneration rather than simply alleviating symptoms with no curative intent. Further research is required to more comprehensively understand the contributions of these pathways to the pathophysiology of depressive disorders to allow for disease modifying treatments to be discovered.

Augmentation of antidepressant effects of venlafaxine by agomelatine in mice are independent of kynurenine pathway

Agomelatine is a novel antidepressant with agonistic actions at melatonergic (MT1 and MT2 receptors) and antagonistic actions at 5HT-2C receptors. Venlafaxine, a serotonin norepinephrine reuptake inhibitor, is a widely prescribed drug in depression. The present study evaluated the low dose combinations of venlafaxine and agomelatine in chronic forced swim test (chronic FST) and tail suspension test (TST) in mice. Further, the effect of above drugs and their combination was evaluated on serum pro-inflammatory cytokines and hippocampal indole amine 2, 3 dioxygenase (IDO) activity by calculating the ratios of kynurenine/tryptophan (KYN/TRP) and serotonin/tryptophan (5HT/TRP). Treatment of agomelatine (4 mg/kg, i.p.) in combination with venlafaxine (4 mg/kg, i.p.) for 3 weeks showed a significant augmenting effect on both swimming and immobility time in chronic FST and immobility time in TST as compared to animals treated with either drug alone. While venlafaxine (4 mg/kg) reversed the elevated serum levels of IL-1β and IL-6 found in chronically stressed mice, agomelatine (4 and 8 mg/kg) failed to show such a reversal. Agomelatine alone and in combination also failed to reverse the increased activity of IDO as observed by enhanced KYN/TRP and reduced 5HT/TRP seen in chronically stressed mice indicating that the augmented antidepressant effect of venlafaxine by agomelatine is not mediated by pro-inflammatory cytokine-induced activation of IDO and further, kynurenine pathway.

Profile of agomelatine and its potential in the treatment of generalized anxiety disorder

BACKGROUND

Although many generalized anxiety disorder (GAD) patients respond to the available pharmacological treatments, nearly half of them do not present the expected results. Besides, the side effects associated to some drugs have a negative impact on treatment adherence. Therefore, the aim of this review was to report the clinical profile of agomelatine, a selective melatonergic MT1/MT2 receptor agonist with serotonin 5-HT2c receptor antagonist activities, as a potential pharmacological option in the treatment of GAD.

METHODS

We performed a literature review regarding studies that evaluated the use of agomelatine in GAD treatment.

RESULTS

Two short-term, double-blinded studies and one prevention-treatment trial evaluated the efficacy of agomelatine in the treatment of GAD. Agomelatine was associated with higher rates of clinical response and remission, when compared to placebo. In addition, the long-term use of agomelatine decreased the risk of relapse of anxiety symptoms, even for the severely ill patients. Besides, the tolerability was satisfactory with the absence of discontinuation symptoms, as observed in previous studies.

CONCLUSION

The efficacy and tolerability profiles of agomelatine in the treatment of GAD were good. However, the scarce number of trials, the small sample sizes, and the use of patients without any comorbid conditions were some limitations that impaired the generalization of the results in the general population. Nevertheless, agomelatine is an attractive off-label option in the treatment of GAD that needs more conclusive evidences to establish its role in future guidelines.

Agomelatine (S20098) modulates the expression of cytoskeletal microtubular proteins, synaptic markers and BDNF in the rat hippocampus, amygdala and PFC

RATIONALE

Agomelatine is described as a novel and clinical effective antidepressant drug with melatonergic (MT(1)/MT(2)) agonist and 5-HT(2C) receptor antagonist properties. Previous studies suggest that modulation of neuronal plasticity and microtubule dynamics may be involved in the treatment of depression.

OBJECTIVE

The present study investigated the effects of agomelatine on microtubular, synaptic and brain-derived neurotrophic factor (BDNF) proteins in selected rat brain regions.

METHODS

Adult male rats received agomelatine (40 mg/kg i.p.) once a day for 22 days. The pro-cognitive effect of agomelatine was tested in the novel object recognition task and antidepressant activity in the forced swimming test. Microtubule dynamics markers, microtubule-associated protein type 2 (MAP-2), phosphorylated MAP-2, synaptic markers [synaptophysin, postsynaptic density-95 (PSD-95) and spinophilin] and BDNF were measured by Western blot in the hippocampus, amygdala and prefrontal cortex (PFC).

RESULTS

Agomelatine exerted pro-cognitive and antidepressant activity and induced molecular changes in the brain areas examined. Agomelatine enhanced microtubule dynamics in the hippocampus and to a higher magnitude in the amygdala. By contrast, in the PFC, a decrease in microtubule dynamics was observed. Spinophilin (dendritic spines marker) was decreased, and BDNF increased in the hippocampus. Synaptophysin (presynaptic) and spinophilin were increased in the PFC and amygdala, while PSD-95 (postsynaptic marker) was increased in the amygdala, consistent with the phenomena of synaptic remodelling.

CONCLUSIONS

Agomelatine modulates cytoskeletal microtubule dynamics and synaptic markers. This may play a role in its pharmacological behavioural effects and may result from the melatonergic agonist and 5-HT(2C) antagonist properties of the compound.

Boosting serotonin in the brain: is it time to revamp the treatment of depression?

Abnormalities in serotonin systems are presumably linked to various psychiatric disorders including schizophrenia and depression. Medications intended for these disorders aim to either block the reuptake or the degradation of this neurotransmitter. In an alternative approach, efforts have been made to enhance serotonin levels through dietary manipulation of precursor levels with modest clinical success. In the last 30 years, there has been little improvement in the pharmaceutical management of depression, and now is the time to revisit therapeutic strategies for the treatment of this disease. Tryptophan hydroxylase (TPH) catalyzes the first and rate-limiting step in the biosynthesis of serotonin. A recently discovered isoform, TPH2, is responsible for serotonin biosynthesis in the brain. Learning how to activate this enzyme (and its polymorphic versions) may lead to a new, more selective generation of antidepressants, able to regulate the levels of serotonin in the brain with fewer side effects.

Efficacy of agomelatine in major depressive disorder: meta-analysis and appraisal

Agomelatine is the first approved antidepressant that mediates its activity through the melatoninergic pathway rather than the monoaminergic system. This meta-analysis aims to summarize an up-to-date report on the efficacy of agomelatine in major depressive disorder. Archives of published results in PubMed, CINAHL, Cochrane Library, EMBASE and PsycINFO databases were searched for randomized double-blind trials comparing agomelatine against placebo or antidepressant in major depressive disorder. Change in severity of depression as a result of intervention was the main outcome measure. Data necessary to compute the standardized mean difference (SMD) of this outcome and additional sample parameters that were likely to influence the main outcome were extracted for each selected studies. Summary effect sizes of various groups and subgroups were computed from SMDs between agomelatine and control (placebo or antidepressants) arms. There were nine trials involving 3943 severe cases of depression on agomelatine (n=2390) and either placebo (n=689) or antidepressants (n=864). Agomelatine (n=1274) stood superior to placebo (n=689) by a small margin (SMD -0.26, p=3.48×10-11) and the superiority of agomelatine (n=834, dose ≥ 25 mg/d) over antidepressants (paroxetine, fluoxetine, sertraline, venlafaxine; n=864) was even smaller (SMD -0.11, p=0.02). Although there is evidence of the superiority of agomelatine over placebo and selected antidepressants, it is questionable whether the magnitude of effect size is clinically significant and sample characteristics are relevant to the general patient population with major depressive disorder.

Agomelatine in unipolar depression in clinical practice: a retrospective chart review

Agomelatine (Valdoxan), a synthetic melatonergic receptor agonist at the MT1 and MT2 receptors, was first used in the management of sleep disorder. Its 5HT2C receptor antagonistic properties support its antidepressant potential. It is currently licensed in the UK, Europe and USA for the treatment of major depressive disorder. Although the randomized controlled evidence base for its use is growing, there are no retrospective, naturalistic studies available. We aimed to determine the tolerability and clinical effectiveness of agomelatine in unipolar depression. We also examined whether being refractory to treatment altered clinical outcome. Forty-eight patient records were examined. Twenty-five percent were treatment refractory: Clinical Global Impression (CGI) Severity score at the start of treatment was 3.81 compared with 3.38 at the end of treatment. Fifty-four percent improved at least minimally; only 12.5% were much or very much improved. Treatment-refractory patients had a poorer outcome with higher discontinuation rates and lower CGI Improvement (p = 0.0205). Treatment-refractory patients also had a higher CGI Severity score at the end of treatment than at treatment commencement (3.92 versus 3.75), although this was not statistically significant.

Chronic agomelatine and fluoxetine induce antidepressant-like effects in H/Rouen mice, a genetic mouse model of depression

The novel antidepressant agomelatine behaves as an agonist at melatonergic MT(1) and MT(2) receptors and as an antagonist at serotonin 5-HT(2C) receptors. This study investigated the effects of agomelatine and fluoxetine in a genetic model of depression called H/Rouen mice Male and female H/Rouen (helpless line) and NH/Rouen (nonhelpless line) mice, received once daily for 3 weeks agomelatine (10 and 50 mg/kgi.p.), fluoxetine (10 mg/kgi.p.) or vehicle. Immobility duration in the tail suspension test (TST) was assessed on day 1 (D1), day 8 (D8), day 15 (D15) and day 22 (D22). Locomotor activity in a novel environment was assessed on day 18 (D18) and anhedonia (2-bottle sucrose preference test) was considered after the end of chronic treatment, from days 22 to 25. Agomelatine (50 mg/kg) significantly reduced immobility at D15 (p<0.01), and D22 (p<0.001) in treated H/Rouen mice whereas agomelatine at 10 mg/kg did not induce a statistically significant change. Fluoxetine reduced immobility at D8 (p<0.01), D15 (p<0.001) and D22 (p<0.001). Locomotor activity was unchanged in all treated groups as compared to vehicle groups. In the sucrose test, there was a significant decrease in sucrose preference in H/Rouen mice compared with NH/Rouen mice receiving vehicle. Both agomelatine doses (10 mg/kg (p=0.05) and 50 mg/kg (p<0.001) as well as fluoxetine (p<0.001) significantly increased the sucrose preference in H/Rouen mice as compared with H/Rouen mice that had received vehicle. These data indicate that the novel antidepressant agomelatine has antidepressant-like properties in H/Rouen mice, a genetic model of depression.

Memory facilitating effects of agomelatine in the novel object recognition memory paradigm in the rat

The aim of the present study was to evaluate the effects of agomelatine, an antidepressant with melatonergic agonist and 5-HT(2C) antagonist properties, in the rat novel object recognition (NOR) task, a model of short-term episodic memory. To assess the potential involvement of its chronobiotic activity, single intraperitoneal administration of agomelatine and NOR testing were performed either in the evening or in the morning. In both conditions, using a 24h retention interval, vehicle-treated rats did not discriminate between the novel and the familiar object (recognition index was not different from chance performance) while object memory performance of rats treated with agomelatine either in the evening (10 and 40mg/kg) or in the morning (2.5, 10, and 40mg/kg) was significantly improved. Moreover, the selective 5-HT(2C) antagonist SB 242,084 (0.63, 2.5, and 10mg/kg) and melatonin (2.5, 10, and 40mg/kg) displayed also memory facilitating effects in both administration conditions. Finally, thioperamide used as positive reference compound to validate the experimental conditions, demonstrated a memory facilitating effect. In conclusion, agomelatine was shown to possess memory facilitating effects in the rat NOR task and both melatonergic agonist and 5-HT(2C) antagonist properties could be involved in these effects.

Neuronal-immune interactions in mediating stress effects in the etiology and course of schizophrenia: role of the amygdala in developmental co-ordination

Stress, in its many forms, is long associated with the etiology and course of schizophrenia. The mechanisms mediating the impacts of stress are not fully elucidated. Here it is proposed that stress induced cortisol alters kynurenic acid (KA) and quinolinic acid (QA) in the cortex and amygdala/striatum, respectively. These effects are significantly modulated by BAG-1 (bcl-2 associated anthanogene) and involve ROS, IL-18, and the induction of IDO (indoleamine 2,3-dioxygenase). The kynurenine pathway (KP) products response to stress seems to mediate both prenatal etiology and symptom course in adulthood. It is suggested that the effects of cortisol and quinolinic acid in the amygdala, coupled to an increase in dopamine efflux, mediate amygdala driven developmental changes in the cortex and VTA/N.Accumbens junction. This change in patterned brain activity co-ordinates alterations in motivated behaviour and thought outputs. Such developmental alterations determine changes in sensory-amygdala interactions, readily allowing developmental links to changes in lateral inhibition and pre-pulse inhibition. Decreases in vitamin D3 and melatonin further potentiate such stress induced changes. The likely involvement of glia in mediating increases in the KP products suggests that adaptation to stress is driven by neuronal activity as a form of glia to glia communication.