Behavioral and neurochemical effects of 5-(4-[4-(5-Cyano-3-indolyl)-butyl)-butyl]-1-piperazinyl)-benzofuran-2-carboxamide (EMD 68843): a combined selective inhibitor of serotonin reuptake and 5-hydroxytryptamine(1A) receptor partial agonist

Synthesis and biological evaluation of multimodal monoaminergic arylpiperazine derivatives with potential antidepressant profile

Depression is a common psychiatric disorder with an estimated global prevalence of 4.4 %. Here, we designed a series of new multimodal monoaminergic arylpiperazine derivatives using a pharmacophore hybrid approach and synthesized them for the treatment of depression. Molecular docking was employed to elucidate the differences in activity and selectivity of the corresponding compounds on SERT, NET, and DAT. In vitro experiments demonstrated that compound A3 has a relatively balanced multi-target activity profile with SERT reuptake inhibition (IC50 = 12 nM), NET reuptake inhibition (IC50 = 78 nM), DAT reuptake inhibition (IC50 = 135 nM), and 5-HT1AR agonism (EC50 = 34 nM). Pharmacokinetic experiments revealed that A3 exhibited excellent bioavailability and low clearance in mice. Subsequent behavioral experiments further confirmed its significant antidepressant effects. These results further highlight the rationality of our design strategy.

Involvement of kynurenine pathway and N-methyl-d-aspartate receptors in the antidepressant-like effect of vilazodone in the tail suspension test in mice

The present study evaluated the antidepressant-like effects of vilazodone using the tail suspension test in mice. We also investigated the contribution of kynurenine pathway and N-methyl-d-aspartate receptors to this effect. For this purpose, we pretreated animals with sub-effective doses of L-kynurenine, 3-hydroxykynurenine, or quinolinic acid. We then assessed the immobility time, an indicative measure of depressive-like behavior, in the tail suspension test. We also evaluated the possible effects of sub-effective doses of vilazodone combined with sub-effective doses of ketamine (N-methyl-d-aspartate receptor antagonist) in a separate group. Vilazodone (3mg/kg, intraperitoneal) significantly reduced immobility time in the tail suspension test. L-kynurenine (1.7 mg/kg, intraperitoneal), 3-hydroxykynurenine (10 mg/kg, intraperitoneal), and quinolinic acid (3 nmol/site, intracerebroventricular) significantly increased the immobility time in the tail suspension test. The antidepressant-like effects of vilazodone (3mg/kg, intraperitoneal) were inhibited by pre-treatment with non-effective doses of L-kynurenine (0.83 mg/kg, intraperitoneal), 3-hydroxykynurenine (3.33 mg/kg, intraperitoneal), or quinolinic acid (1 nmol/site, intracerebroventricular). Pretreatment of mice with sub-effective doses of ketamine (1 mg/kg, intraperitoneal) optimized the action of a sub-effective dose of vilazodone (0.3mg/kg, intraperitoneal) and reduced the immobility time in the tail suspension test. None of the drugs used in this study induced any changes in locomotor activity in the open field test. The results showed that vilazodone induced an antidepressant-like effect in the tail suspension test, which may be mediated through an interaction with the kynurenine pathway and N-methyl-d-aspartate receptors.

The effects of Vilazodone, YL-0919 and Vortioxetine in hemiparkinsonian rats

Parkinson's disease is a neurodegenerative disease often characterized by motor deficits and most commonly treated with dopamine replacement therapy. Despite its benefits, chronic use of L-DOPA results in abnormal involuntary movements known as L-DOPA-induced dyskinesia. Growing evidence shows that with burgeoning dopamine cell loss, neuroplasticity in the serotonin system leads to the development of L-DOPA-induced dyskinesia through the unregulated uptake, conversion, and release of L-DOPA-derived dopamine into the striatum. Previous studies have shown that coincident 5-HT_1A agonism and serotonin transporter inhibition may have anti-dyskinetic potential. Despite this, few studies have explicitly focused on targeting both 5-HT_1A and the serotonin transporter. The present study compares the 5-HT compounds Vilazodone, YL-0919, and Vortioxetine which purportedly work as simultaneous 5-HT_1A receptor agonists and SERT blockers. To do so, adult female Sprague Dawley rats were rendered hemiparkinsonian and treated daily for two weeks with L-DOPA to produce stable dyskinesia. The abnormal involuntary movements and forehand adjusting step tests were utilized as measurements for L-DOPA-induced dyskinesia and motor performance in a within-subjects design. Lesion efficacy was determined by analysis of striatal monoamines via high-performance liquid chromatography. Compounds selective for 5-HT_1A/SERT target sites including Vilazodone and Vortioxetine significantly reduced L-DOPA-induced dyskinesia without compromising L-DOPA pro-motor efficacy. In contrast, YL-0919 failed to reduce L-DOPA-induced dyskinesia, with no effects on L-DOPA-related improvements. Collectively, this work supports pharmacological targeting of 5-HT_1A/SERT to reduce L-DOPA-induced dyskinesia. Additionally, this further provides evidence for Vilazodone and Vortioxetine, FDA-approved compounds, as potential adjunct therapeutics for L-DOPA-induced dyskinesia management in Parkinson's patients.

Sexual dysfunction with major depressive disorder and antidepressant treatments: impact, assessment, and management

INTRODUCTION

Sexual dysfunction (SD) is a symptom of depression in ≈70% of patients presenting with major depressive disorder (MDD). Antidepressant medications (AD) and adjunctive treatments may further contribute to SD and complicate evaluation and management.

AREAS COVERED

A systematic literature search of PubMed, Ovid MEDLINE and Cochrane databases for MDD, SD, classes of antidepressants, etc. was performed with a focus on 2014 to June 2021. SSRIs are associated with 70% treatment-emergent sexual dysfunction (TESD), SNRIs and tricyclics have rates of TESD of 40 - 45%, and antidepressant medications without SRI effects or with additional unique mechanisms of action have rates similar to placebo (<10%). Appropriate assessment at baseline and throughout treatment, consideration of patient preferences in prescribing, addressing modifiable factors (comorbid medical/psychiatric conditions, substances, relationship difficulties), and utilizing management strategies of switching to an AD with less SD, adding an antidote/adjunctive therapy or lowering the dose are discussed.

EXPERT OPINION

MDD and antidepressant treatment contribute to SD in a high percentage of patients. Treating to remission reduces SD as a symptom of depression. Frequent assessment and targeted management strategies may be effective in preventing or addressing SD. Secondary outcomes like impact on adherence, relationships and self-image should also be considered.

Role of 5-HT1A Receptor in Vilazodone-Mediated Suppression of L-DOPA-Induced Dyskinesia and Increased Responsiveness to Cortical Input in Striatal Medium Spiny Neurons in an Animal Model of Parkinson's Disease

L-DOPA therapy in Parkinson’s disease (PD) is limited due to emerging L-DOPA-induced dyskinesia. Research has identified abnormal dopamine release from serotonergic (5-HT) terminals contributing to this dyskinesia. Selective serotonin reuptake inhibitors (SSRIs) or 5-HT receptor (5-HTr) agonists can regulate 5-HT activity and attenuate dyskinesia, but they often also produce a loss of the antiparkinsonian efficacy of L-DOPA. We investigated vilazodone, a novel multimodal 5-HT agent with SSRI and 5-HTr_1A partial agonist properties, for its potential to reduce dyskinesia without interfering with the prokinetic effects of L-DOPA, and underlying mechanisms. We assessed vilazodone effects on L-DOPA-induced dyskinesia (abnormal involuntary movements, AIMs) and aberrant responsiveness to corticostriatal drive in striatal medium spiny neurons (MSNs) measured with in vivo single-unit extracellular recordings, in the 6-OHDA rat model of PD. Vilazodone (10 mg/kg) suppressed all subtypes (axial, limb, orolingual) of AIMs induced by L-DOPA (5 mg/kg) and the increase in MSN responsiveness to cortical stimulation (shorter spike onset latency). Both the antidyskinetic effects and reversal in MSN excitability by vilazodone were inhibited by the 5-HTr_1A antagonist WAY-100635, demonstrating a critical role for 5-HTr_1A in these vilazodone actions. Our results indicate that vilazodone may serve as an adjunct therapeutic for reducing dyskinesia in patients with PD.

Early response to trazodone once-a-day in major depressive disorder: review of the clinical data and putative mechanism for faster onset of action

BACKGROUND

Most antidepressants have a delayed onset of action and must be administered for several weeks to generate therapeutic effects. Trazodone is a serotonin antagonist and reuptake inhibitor approved for the treatment of major depressive disorder. The once-a-day (OAD) formulation of trazodone has an improved tolerability profile compared to its conventional formulations. In this study, we systematically reviewed the evidence available for the antidepressant efficacy and early improvement in depressive symptoms with trazodone OAD treatment.

METHOD

We conducted a PubMed database search for randomized controlled trials published from 2005 to 2020.

RESULTS

Two studies, a placebo-controlled and an active-comparator (venlafaxine extended-release or XR) study were found. Both the studies demonstrated that trazodone exhibits antidepressant activity at a starting dose of 150 mg/day and results in statistically significant greater reduction in Hamilton Depression Rating Scale (HAM-D17) scores within 1 week of starting treatment compared to placebo or venlafaxine XR (P < .05). Trazodone also resulted in significant early improvement in the HAM-D17 sleep disturbance factor compared to placebo or venlafaxine XR at day 7 (P < .05). This clinical effect is supported by in vitro proprietary data for the affinity of trazodone for different target receptors. Activity at these receptors may underlie trazodone's fast antidepressant action.

CONCLUSIONS

Trazodone, if properly dosed, can be an effective antidepressant with early onset of action and good tolerability. Future studies designed to specifically evaluate onset and timing of improvement of depressive symptoms remain necessary to confirm and extend these results.

Molecular aspects of depression: A review from neurobiology to treatment

Major depressive disorder (MDD), also known as unipolar depression, is one of the leading causes of disability and disease worldwide. The signs and symptoms are low self‑esteem, anhedonia, feeling of worthlessness, sense of rejection and guilt, suicidal thoughts, among others. This review focuses on studies with molecular-based approaches involving MDD to obtain an integrated, more detailed and comprehensive view of the brain changes produced by this disorder and its treatment and how the Central Nervous System (CNS) produces neuroplasticity to orchestrate adaptive defensive behaviors. This article integrates affective neuroscience, psychopharmacology, neuroanatomy and molecular biology data. In addition, there are two problems with current MDD treatments, namely: 1) Low rates of responsiveness to antidepressants and too slow onset of therapeutic effect; 2) Increased stress vulnerability and autonomy, which reduces the responses of currently available treatments. In the present review, we encourage the prospection of new bioactive agents for the development of treatments with post-transduction mechanisms, neurogenesis and pharmacogenetics inducers that bring greater benefits, with reduced risks and maximized access to patients, stimulating the field of research on mood disorders in order to use the potential of preclinical studies. For this purpose, improved animal models that incorporate the molecular and anatomical tools currently available can be applied. Besides, we encourage the study of drugs that do not present "classical application" as antidepressants, (e.g., the dissociative anesthetic ketamine and dextromethorphan) and drugs that have dual action mechanisms since they represent potential targets for novel drug development more useful for the treatment of MDD.

5-HT6 receptor agonist and memory-enhancing properties of hypidone hydrochloride (YL-0919), a novel 5-HT1A receptor partial agonist and SSRI

Most current antidepressants are lacking a pro-cognition effect or even impair cognition as a side effect, and there are few effective psychopharmacological options that improve cognitive dysfunction in depression. Our previous studies revealed that hypidone hydrochloride (YL-0919), a novel 5-HT_1A receptor partial agonist and SSRI, has antidepressant- and anxiolytic-like effects. Here, further studies found that YL-0919, but not vilazodone (a 5-HT_1A receptor partial agonist and SSRI), exerted a significant memory-enhancing effect in the Morris water maze, object recognition test and step-down passive avoidance task. Because the 5-HT₆ receptor has emerged as an interesting drug target to improve cognition, we investigated the target profile of YL-0919 using radioligand binding assays, [³⁵S]-GTPγS binding and cAMP stimulation assays. YL-0919 was found to act as a highly effective, full agonist of 5-HT₆ receptors. Finally, we observed that the memory-enhancing activities of YL-0919 were completely reversed after co-administration of SB271046 (a selective 5-HT₆ receptor antagonist) at a dose that does not alter cognition. In summary, the findings of the current study suggest that YL-0919 has clear memory-enhancing effects, which might be at least partially mediated by 5-HT₆ receptor activation.

Can we increase speed and efficacy of antidepressant treatments? Part I: General aspects and monoamine-based strategies

Major depressive disorder (MDD) is a severe psychiatric syndrome with high prevalence and socioeconomic impact. Current antidepressant treatments are based on the blockade of serotonin (5-hydroxytryptamine, 5-HT) and/or noradrenaline transporters. These drugs show slow onset of clinical action and limited efficacy, partly due to the activation of physiological negative feed-back mechanisms operating through autoreceptors (5-HT_1A, 5-HT_1B, α₂-adrenoceptors) and postsynaptic receptors (e.g., 5-HT₃). As a result, clinically-relevant doses of reuptake inhibitors increase extracellular (active) 5-HT concentrations in the midbrain raphe nuclei but not in forebrain, as indicated by rodent microdialysis studies and by PET-scan studies in primate/human brain. The prevention of these self-inhibitory mechanisms by antagonists of the above receptors augments preclinical and clinical antidepressant effects. Hence, the mixed ß-adrenoceptor/5-HT_1A antagonist pindolol accelerated, and in some cases enhanced, the clinical action of selective serotonin reuptake inhibitors (SSRI). This strategy has been incorporated into two new multi-target antidepressant drugs, vilazodone and vortioxetine, which combine 5-HT reuptake inhibition and partial agonism at 5-HT_1A receptors. Vortioxetine shows also high affinity for other 5-HT receptors, including excitatory 5-HT₃ receptors located in cortical and hippocampal GABA interneurons. 5-HT₃ receptor blockade by vortioxetine enhances pyramidal neuron activity in prefrontal cortex as well as cortical and hippocampal 5-HT release. It is still too soon to know whether these new antidepressants will represent a real advance over existing drugs in the real world. However, their development opened the way to future antidepressant drugs based on the prevention of local and distal self-inhibitory mechanisms attenuating monoamine activity.

Efficacy and tolerability of different doses of three new antidepressants for treating major depressive disorder: A PRISMA-compliant meta-analysis

In last decade, the US FDA has approved three new antidepressants: vortioxetine, levomilnacipran, and vilazodone. Many studies have researched the effects of these antidepressants on major depressive disorder (MDD), but they have not determined the optimum dosage. This meta-analysis investigated the efficacies of these three drugs at different dosages in the treatment of MDD. The PubMed, Embase, Cochrane Library, psycINFO, and ClinicalTrials.gov databases were searched to identify relevant literature. The primary outcomes were efficacy [quantified as the change from baseline in total score on the Montgomery-Asberg Depression Rating Scale (MADRS)] and tolerability (discontinuations due to adverse events). The effect size was quantified as the weighted mean difference for continuous data and the risk ratio (RR) for dichotomous data. Overall 22 studies were included. The changes in the MADRS total score were significantly higher for vortioxetine at 5, 10, 20, and 10-20 mg/day than for placebo. The tolerability was significantly worse for 20 mg/day vortioxetine than for placebo (RR = 1.84, 95% confidence interval = 1.13 to 3.02). In addition, increasing the dosage improved the efficacy of vortioxetine but worsened the tolerability. Levomilnacipran and vilazodone at any dosage produced a significantly higher mean change from baseline in the MADRS total score and a worse tolerability than for placebo. In conclusion, considering both efficacy and tolerability, 10 mg/day vortioxetine might be optimal for the treatment of MDD. The long-term efficacy and safety of vortioxetine needed to be investigated, and more studies of levomilnacipran and vilazodone are needed to define their optimal dosages.

Identification and characterization of vilazodone metabolites in rats and microsomes by ultrahigh-performance liquid chromatography/quadrupole time-of-flight tandem mass spectrometry

RATIONALE

Vilazodone is a selective serotonin reuptake inhibitor (SSRI) used for the treatment of major depressive disorder (MDD). An extensive literature search found few reports on the in vivo and in vitro metabolism of vilazodone. Therefore, we report a comprehensive in vivo and in vitro metabolic identification and structural characterization of vilazodone using ultrahigh-performance liquid chromatography/quadrupole time-of-flight tandem mass spectrometry (UPLC/Q-TOF/MS/MS) and in silico toxicity study of the metabolites.

METHODS

To identify in vivo metabolites of vilazodone, blood, urine and faeces samples were collected at different time intervals starting from 0 h to 48 h after oral administration of vilazodone to Sprague-Dawley rats. The in vitro metabolism study was conducted with human liver microsomes (HLM) and rat liver microsomes (RLM). The samples were prepared using an optimized sample preparation approach involving protein precipitation followed by solid-phase extraction. The metabolites have been identified and characterized by using LC/ESI-MS/MS.

RESULTS

A total of 12 metabolites (M1-M12) were identified in in vivo and in vitro matrices and characterized by LC/ESI-MS/MS. The majority of the metabolites were observed in urine, while a few metabolites were present in faeces and plasma. Two metabolites were observed in the in vitro study. A semi-quantitative study based on percentage counts shows that metabolites M11, M6 and M8 were observed in higher amounts in urine, faeces and plasma, respectively.

CONCLUSIONS

The structures of all the 12 metabolites were elucidated by using LC/ESI-MS/MS. The study suggests that vilazodone was metabolized via hydroxylation, dihydroxylation, glucuronidation, oxidative deamination, dealkylation, dehydrogenation and dioxidation. All the metabolites were screened for toxicity using an in silico tool.

Vilazodone for the Treatment of Depression: An Update

Vilazodone is a novel antidepressant having a selective serotonin (5-HT) reuptake inhibitor and 5-HT1A receptor partial agonist profile, so it has been regarded as a serotonin partial agonist-reuptake inhibitor (SPARI). We aimed to provide Vilazodone's clinical implications mainly by reviewing published clinical trials. Vilazodone has been speculated to have three potential benefits including faster onset of action, greater efficacy, and better tolerability owning to its SPARI properties. However, no studies conducted so far have directly proven the above speculations. Five initial phase II trials failed to distinguish vilazodone from placebo in the treatment of MDD, but 4 randomized clinical trials (RCT), 3 post-hoc or pooled analysis, 1 long-term open label study, and a meta-analysis showed vilazodone's superior efficacy over placebo. The studies also showed vilazodone is generally safe and tolerable. However, diarrhea, nausea, headache, dizziness, dry mouth, and insomnia warrant close attention in clinical practice because they have been constantly noted throughout the clinical studies. 2 RCTs recently documented the efficacy and safety of vilazodone in patients with generalized anxiety disorder, which could be a start of broadening vilazodone's usage or FDA approval in diverse anxiety disorders.

The Preclinical and Clinical Effects of Vilazodone for the Treatment of Major Depressive Disorder

INTRODUCTION

Major depressive disorder (MDD) is the leading cause of disability worldwide, and according to the STAR*D trial, only 33% of patients with MDD responded to initial drug therapy. Augmentation of the leading class of antidepressant treatment, selective serotonin reuptake inhibitors (SSRIs), with the 5-HT1A receptor agonist buspirone has been shown to be effective in treating patients that do not respond to initial SSRI therapy. This suggests that newer treatments may improve the clinical picture of MDD. The US Food and Drug Administration (FDA) approved the antidepressant drug vilazodone (EMD 68843), a novel SSRI and 5-HT1A receptor partial agonist. Vilazodone has a half-life between 20-24 hours, reaches peak plasma concentrations at 3.7-5.3 hours, and is primarily metabolized by the hepatic CYP450 3A4 enzyme system.

AREAS COVERED

The authors review the preclinical and clinical profile of vilazodone. The roles of serotonin, the 5-HT1A receptor, and current pharmacotherapy approaches for MDD are briefly reviewed. Next, the preclinical pharmacological, behavioral, and physiological effects of vilazodone are presented, followed by the pharmacokinetic properties and metabolism of vilazodone in humans. Last, a brief summary of the main efficacy, safety, and tolerability outcomes of clinical trials of vilazodone is provided.

EXPERT OPINION

Vilazodone has shown efficacy versus placebo in improving depression symptoms in several double-blind, placebo-controlled trials. The long-term safety and tolerability of vilazodone treatment has also been established. Further studies are needed that directly compare patients treated with an SSRI (both with and without an adjunctive 5-HT1A partial agonist) versus patients treated with vilaozodone.

Differential effects of vilazodone versus citalopram and paroxetine on sexual behaviors and serotonin transporter and receptors in male rats

RATIONALE

Sexual side effects are commonly associated with selective serotonin reuptake inhibitor (SSRI) treatment. Some evidence suggest that activation of 5-HT1A receptors attenuates SSRI-induced sexual dysfunction.

OBJECTIVE

This study in male rats compared the effects of vilazodone, an antidepressant with SSRI and 5-HT1A receptor partial agonist activity, with other prototypical SSRIs (citalopram and paroxetine) on sexual behaviors and 5-HT receptors (5-HT1A and 5-HT2A) and transporter (5-HTT) levels in select forebrain regions of the limbic system using quantitative autoradiography.

METHODS

Rats received vilazodone (1, 3, and 10 mg/kg), citalopram (10 and 30 mg/kg), or paroxetine (10 mg/kg) treatment for 14 days. Sexual behaviors (frequency and latency of mounts, intromissions, and ejaculations) were measured in the presence of an estrous female rat on days 1 (acute), 7 (subchronic), and 14 (chronic).

RESULTS

Vilazodone-treated rats exhibited no sexual dysfunction compared with controls; in contrast, the citalopram- and paroxetine-treated rats exhibited impaired copulatory and ejaculatory behaviors after subchronic and chronic treatments. Chronic vilazodone treatment markedly decreased 5-HT1A receptor levels in cortical and hippocampal regions, while the SSRIs increased levels of this receptor in similar regions. All chronic treatments reduced 5-HTT levels across the forebrain; however, the magnitude of the decrease was considerably smaller for vilazodone than for the SSRIs.

CONCLUSIONS

The current studies showed that chronic treatment with vilazodone, in contrast to citalopram and paroxetine, was not associated with diminished sexual behaviors in male rats, which may be related to the differential effects of vilazodone on 5-HT1A receptor and 5-HTT levels relative to conventional SSRIs.

Functional Selectivity and Antidepressant Activity of Serotonin 1A Receptor Ligands

Serotonin (5-HT) is a monoamine neurotransmitter that plays an important role in physiological functions. 5-HT has been implicated in sleep, feeding, sexual behavior, temperature regulation, pain, and cognition as well as in pathological states including disorders connected to mood, anxiety, psychosis and pain. 5-HT1A receptors have for a long time been considered as an interesting target for the action of antidepressant drugs. It was postulated that postsynaptic 5-HT1A agonists could form a new class of antidepressant drugs, and mixed 5-HT1A receptor ligands/serotonin transporter (SERT) inhibitors seem to possess an interesting pharmacological profile. It should, however, be noted that 5-HT1A receptors can activate several different biochemical pathways and signal through both G protein-dependent and G protein-independent pathways. The variables that affect the multiplicity of 5-HT1A receptor signaling pathways would thus result from the summation of effects specific to the host cell milieu. Moreover, receptor trafficking appears different at pre- and postsynaptic sites. It should also be noted that the 5-HT1A receptor cooperates with other signal transduction systems (like the 5-HT1B or 5-HT2A/2B/2C receptors, the GABAergic and the glutaminergic systems), which also contribute to its antidepressant and/or anxiolytic activity. Thus identifying brain specific molecular targets for 5-HT1A receptor ligands may result in a better targeting, raising a hope for more effective medicines for various pathologies.

Developments in the field of antidepressants, where do we go now?

Major depression is a severe psychiatric syndrome with very high prevalence and socio-economic impact. Its pathophysiology is poorly known, yet several neurotransmitter systems and brain areas have been implicated. Selective serotonin (5-hydroxytryptamine, 5-HT) reuptake inhibitors (SSRI) and serotonin and norepinephrine reuptake inhibitors (SNRI) are most used antidepressant treatments. However, these drugs show slow onset of action and limited efficacy, making necessary the use of drug augmentation strategies or more aggressive interventions. Two important observations have emerged in recent years indicating that more rapid and effective antidepressant treatments are possible. Hence, the deep brain stimulation (DBS) of ventral anterior (subgenual) cingulate cortex (Cg25) evokes rapid mood improvements in subgroups of treatment-resistant depressive patients, likely mediated by a functional remodelling of cortico-limbic circuits. On the other hand, the non-competitive NDMA receptor antagonist ketamine can also evoke rapid (e.g., 2h) and persistent (up to 1 wk) improvements in some treatment-resistant patients. Moreover, recent preclinical observations indicate the antidepressant capacity of mGluR agents. Overall, this supports the usefulness of glutamatergic transmission as a new area in antidepressant drug development. On the monoamine side, new preclinical and clinical research should clarify the different roles played by 5-HT receptors in depression as well as the brain areas and circuits responsible for therapeutic improvement. This will lead to the synthesis of new agents blocking the serotonin (and possibly norepinephrine) transporter which will also activate or block 5-HT receptors playing respectively positive (e.g., postsynaptic 5-HT1A, 5-HT4) or negative (e.g., presynaptic 5-HT1A,/1B, 5-HT2A, 5-HT2C,5-HT3, etc.) roles in antidepressant effects.

Learning from the past and looking to the future: Emerging perspectives for improving the treatment of psychiatric disorders

Modern neuropsychopharmacology commenced in the 1950s with the serendipitous discovery of first-generation antipsychotics and antidepressants which were therapeutically effective yet had marked adverse effects. Today, a broader palette of safer and better-tolerated agents is available for helping people that suffer from schizophrenia, depression and other psychiatric disorders, while complementary approaches like psychotherapy also have important roles to play in their treatment, both alone and in association with medication. Nonetheless, despite considerable efforts, current management is still only partially effective, and highly-prevalent psychiatric disorders of the brain continue to represent a huge personal and socio-economic burden. The lack of success in discovering more effective pharmacotherapy has contributed, together with many other factors, to a relative disengagement by pharmaceutical firms from neuropsychiatry. Nonetheless, interest remains high, and partnerships are proliferating with academic centres which are increasingly integrating drug discovery and translational research into their traditional activities. This is, then, a time of transition and an opportune moment to thoroughly survey the field. Accordingly, the present paper, first, chronicles the discovery and development of psychotropic agents, focusing in particular on their mechanisms of action and therapeutic utility, and how problems faced were eventually overcome. Second, it discusses the lessons learned from past successes and failures, and how they are being applied to promote future progress. Third, it comprehensively surveys emerging strategies that are (1), improving our understanding of the diagnosis and classification of psychiatric disorders; (2), deepening knowledge of their underlying risk factors and pathophysiological substrates; (3), refining cellular and animal models for discovery and validation of novel therapeutic agents; (4), improving the design and outcome of clinical trials; (5), moving towards reliable biomarkers of patient subpopulations and medication efficacy and (6), promoting collaborative approaches to innovation by uniting key partners from the regulators, industry and academia to patients. Notwithstanding the challenges ahead, the many changes and ideas articulated herein provide new hope and something of a framework for progress towards the improved prevention and relief of psychiatric and other CNS disorders, an urgent mission for our Century.

Vilazodone for the treatment of major depressive disorder: an evidence-based review of its place in therapy

INTRODUCTION

It has clearly been demonstrated that depressive disorders constitute a major worldwide public health problem, with massive economic and quality-of-life consequences. Existing pharmacological treatments have limited efficacy, with only about a third of patients achieving remission on any one medication. Delayed onset of action and variable tolerability contribute to this limited efficacy. Vilazodone, introduced in the US in 2011, has been described as the first member of the serotonin partial agonist-reuptake inhibitor (SPARI) class of medications, combining serotonin-reuptake inhibition with 5-HT1A partial agonism. This agent could potentially have benefits for subgroups of depressed patients, including depressed patients with comorbid anxiety and patients with anxiety disorders, and might have fewer sexual side effects than selective serotonin-reuptake inhibitors (SSRIs).

AIMS

We reviewed existing clinical trials that assess the benefits of vilazodone for treatment of major depression.

EVIDENCE REVIEW

In clinical trials, including two Phase III studies and two Phase IV studies, vilazodone has been shown to have efficacy greater than placebo on the Montgomery-Åsberg Depression Rating Scale, comparable efficacy to citalopram, and continued benefit after 52 weeks of treatment. The safety profile for vilazodone is comparable to other SSRI medications, and tolerability also appears generally comparable to other SSRI medications.

PLACE IN THERAPY

Vilazodone, which has been described as the first-of-class SPARI medication, may potentially have benefits for subgroups of patients, particularly those depressed individuals with coexisting anxiety symptoms or anxiety disorders. However, convincing evidence for these benefits has as yet not been published.

Vilazodone for the treatment of major depressive disorder: focusing on its clinical studies and mechanism of action

We tried to review and update clinical and preclinical studies evaluating vilazodone's role as an antidepressant for patients with major depressive disorder (MDD). In terms of its mechanism of actions, we sought to elaborate them mainly through preclinical animal studies. A data search was conducted in November 1, 2013, using the key terms "vilazodone" or "Viibryd," in PubMed and Medline databases. All published and unpublished studies are included and citations from publications were also reviewed for additional references. Five unpublished, phase-II and two pivotal published phase-III clinical trials with nearly identical design (8-week, double-blind, randomized, and placebo-controlled) investigated efficacy of vilazodone, were found for the treatment of patients with MDD. Two post-hoc studies and one long-term open study were also included. Data were thoroughly reviewed to incorporate the pharmacology, action mechanism, efficacy and safety for the vilazodone in the treatment of major depressive disorder. Vilazodone is an antidepressant with novel mechanism of action because its chemical structure is unrelated to conventional antidepressant, and it has a selective serotonin (5-HT) reuptake inhibitor and 5-HT1A receptor partial agonist profile. Vilazodone is an effective and safe treatment option with its novel action mechanisms for patients with depression. Its putative benefits compared with other antidepressants must be thoroughly studied in adequately-powered and well-designed future clinical trials.

A review of the clinical efficacy, safety and tolerability of the antidepressants vilazodone, levomilnacipran and vortioxetine

INTRODUCTION

As a leading cause of disability, major depressive disorder (MDD) is characterized by reduced quality of life and altered functioning. Current pharmaceutical treatment options are limited in their success by modest effects and adverse events that often lead to discontinuation. One current trend in antidepressant development is to combine inhibition of the serotonin transporter with other pharmacological targets, including the norepinephrine transporter or different serotonin receptors.

AREAS COVERED

In a span of < 3 years, the FDA approved three new antidepressants for the treatment of MDD: vilazodone in January 2011, levomilnacipran in July 2013 and vortioxetine in September 2013. This article reviews the efficacy, safety and tolerability of these three drugs mainly from the Phase III trial data.

EXPERT OPINION

All three drugs are effective in the treatment of MDD, but data comparing them to other antidepressants is currently lacking. Vilazodone was proposed to produce a more rapid onset and have fewer sexual side effects but neither effect has been conclusively shown. Levomilnacipran appears to be effective in improving functional impairment, including both social and work functioning. Vortioxetine is currently the only drug of the three with proven efficacy in elderly patients. It also appears to have cognitive enhancing properties which are largely independent of improved depressive symptoms. Overall, these drugs represent a promising step forward in antidepressant drug development.

Faster, better, stronger: towards new antidepressant therapeutic strategies

Major depression is a highly prevalent disorder and is predicted to be the second leading cause of disease burden by 2020. Although many antidepressant drugs are currently available, they are far from optimal. Approximately 50% of patients do not respond to initial first line antidepressant treatment, while approximately one third fail to achieve remission following several pharmacological interventions. Furthermore, several weeks or months of treatment are often required before clinical improvement, if any, is reported. Moreover, most of the commonly used antidepressants have been primarily designed to increase synaptic availability of serotonin and/or noradrenaline and although they are of therapeutic benefit to many patients, it is clear that other therapeutic targets are required if we are going to improve the response and remission rates. It is clear that more effective, rapid-acting antidepressants with novel mechanisms of action are required. The purpose of this review is to outline the current strategies that are being taken in both preclinical and clinical settings for identifying superior antidepressant drugs. The realisation that ketamine has rapid antidepressant-like effects in treatment resistant patients has reenergised the field. Further, developing an understanding of the mechanisms underlying the rapid antidepressant effects in treatment-resistant patients by drugs such as ketamine may uncover novel therapeutic targets that can be exploited to meet the Olympian challenge of developing faster, better and stronger antidepressant drugs.

Mechanism of action of the bimodal antidepressant vilazodone: evidence for serotonin1A-receptor-mediated auto-augmentation of extracellular serotonin output

RATIONALE

The recently approved antidepressant vilazodone, a serotonin (5-HT)1A receptor partial agonist/selective 5-HT reuptake inhibitor offers new possibilities to study the underlying mechanisms of depression pharmacotherapy and of 5-HT augmenting antidepressants.

OBJECTIVE

The role of the 5-HT1A receptor with respect to the regulation of 5-HT output in the mechanism of action of vilazodone.

METHOD

We measured 5-HT levels in two subregions of the rat prefrontal cortex by microdialysis, and 5-hydroxytryptophan (5-HTP) accumulation and tissue 5-HT concentrations ex vivo.

RESULTS

Vilazodone-induced maximal 5-HT levels were similar in the medial and the lateral cortex and were up to sixfold higher than those induced by paroxetine, citalopram, or fluoxetine tested in parallel. Depolarization/autoreceptor-insensitive 5-HT release by vilazodone could be excluded. The citalopram (1 μM, locally infused)-induced increase of 5-HT was further increased by vilazodone (1 mg/kg i.p.), but not by citalopram (10 mg/kg i.p.). Unlike fluoxetine, vilazodone-induced extracellular 5-HT output was not potentiated by cotreatment with the 5-HT1A receptor blocker N-[2-(4-{2-methoxyphenyl}-1-piperazinyl)-ethyl]-N-2-pyridinylcyclohexanecarboxamide (WAY 100635). In contrast to fluoxetine, vilazodone exhibited intrinsic 5-HT1A agonist activity: it reduced, similar to (±)-8-hydroxy-2-(dipropylamino)-tetralin (8-OH-DPAT), 5-HTP accumulation in striatum and n. raphe of reserpinized rats. Hence, vilazodone's agonistic actions must be 5-HT1A receptor-related since endogenous 5-HT is lacking in the reserpine-depleted animal.

CONCLUSIONS

In spite of high intrinsic 5-HT1A activity in reserpinized rats, the net effect of vilazodone at release-regulating 5-HT1A autoreceptors must be inhibitory, leading to markedly increased 5-HT output. Another possibility is that vilazodone rapidly desensitizes autoinhibitory 5-HT1A receptors by an unknown mechanism.

Mechanism of action of the SPARI vilazodone: serotonin 1A partial agonist and reuptake inhibitor

Vilazodone is an antidepressant with a novel mechanism of pharmacologic action: serotonin partial agonist reuptake inhibitor (SPARI).

Serotonergic modulation of glutamate neurotransmission as a strategy for treating depression and cognitive dysfunction

Monoamine-based treatments for depression have evolved greatly over the past several years, but shortcomings such as suboptimal efficacy, treatment lag, and residual cognitive dysfunction are still significant. Preclinical and clinical studies using compounds directly targeting glutamatergic neurotransmission present new opportunities for antidepressant treatment, with ketamine having a surprisingly rapid and sustained antidepressant effect that is presumably mediated through glutamate-dependent mechanisms. While direct modulation of glutamate transmission for antidepressant and cognition-enhancing actions may be hampered by nonspecific effects, indirect modulation through the serotonin (5-HT) system may be a viable alternative approach. Based on localization and function, 5-HT can modulate glutamate neurotransmission at least through the 5-HT1A, 5-HT1B, 5-HT3, and 5-HT7 receptors, which presents a rational pharmacological opportunity for modulating glutamatergic transmission without the direct use of glutamatergic compounds. Combining one or more of these glutamate-modulating 5-HT targets with 5-HT transporter inhibition may offer new therapeutic opportunities. The multimodal compounds vortioxetine and vilazodone are examples of this approach with diverse mechanisms, and their different clinical effects will provide valuable insights into serotonergic modulation of glutamate transmission for the potential treatment of depression and associated cognitive dysfunction.

5-HT(1A) [corrected] receptors in mood and anxiety: recent insights into autoreceptor versus heteroreceptor function

RATIONALE

Serotonin (5-HT) neurotransmission is intimately linked to anxiety and depression and a diverse body of evidence supports the involvement of the main inhibitory serotonergic receptor, the serotonin-1A (5-HT(1A)) subtype, in both disorders.

OBJECTIVES

In this review, we examine the function of 5-HT(1A) receptor subpopulations and re-interpret our understanding of their role in mental illness in light of new data, separating both spatial (autoreceptor versus heteroreceptor) and the temporal (developmental versus adult) roles of the endogenous 5-HT(1A) receptors, emphasizing their distinct actions in mediating anxiety and depression-like behaviors.

RESULTS

It is difficult to unambiguously distinguish the effects of different populations of the 5-HT(1A) receptors with traditional genetic animal models and pharmacological approaches. However, with the advent of novel genetic systems and subpopulation-selective pharmacological agents, direct evidence for the distinct roles of these populations in governing emotion-related behavior is emerging.

CONCLUSIONS

There is strong and growing evidence for a functional dissociation between auto- and heteroreceptor populations in mediating anxiety and depressive-like behaviors, respectively. Furthermore, while it is well established that 5-HT(1A) receptors act developmentally to establish normal anxiety-like behaviors, the developmental role of 5-HT(1A) heteroreceptors is less clear, and the specific mechanisms underlying the developmental role of each subpopulation are likely to be key elements determining mood control in adult subjects.

A review of vilazodone, serotonin, and major depressive disorder

Objective: To review the mechanism of selective serotonin reuptake inhibitor (SSRI)–mediated serotonergic neurotransmission, focusing on serotonin 1A (5-HT_1A) autoreceptors, which are proposed to be involved in delaying therapeutic efficacy. Vilazodone was specifically designed to function both as an SSRI and a partial agonist at 5-HT_1A receptors. This combined mechanism is proposed to decrease time to efficacy, minimize sexual side effects, and provide concomitant anxiolytic properties.

Data Sources: A PubMed search of all English-language articles from January 1990 to January 2013 was conducted using the search terms depression and 5-HT_1A, depression and buspirone, depression and pindolol, and vilazodone.

Study Selection: We found 47 articles and abstracts that were selected for inclusion on the basis of information about the pharmacology of 5-HT_1A receptors and the clinical data on pindolol, buspirone, and vilazodone in depression.

Data Extraction: This review summarizes current literature involving antidepressant activity, the role of 5-HT_1A autoreceptors, and clinical trials involving serotonin reuptake inhibition in conjunction with 5-HT_1A agonists and partial agonists, with a focus on vilazodone.

Results:Vilazodone has demonstrated efficacy in 2 large, randomized, double-blind, placebo-controlled trials in major depressive disorder. Results suggest that vilazodone has a low incidence of sexual side effects and is effective in patients with high levels of anxiety. A pooled analysis shows evidence of significant symptom reduction after only 1 week of therapy.

Conclusions: If future studies corroborate the clinical benefits attributed to its mechanism of action, vilazodone may show potential advantages in terms of onset of action, sexual side effects, and anxiolytic activity in patients with major depressive disorder.

Antidepressant-like activity of YL-0919: a novel combined selective serotonin reuptake inhibitor and 5-HT1A receptor agonist

It has been suggested that drugs combining activities of selective serotonin reuptake inhibitor and 5-HT1A receptor agonist may form a novel strategy for higher therapeutic efficacy of antidepressant. The present study aimed to examine the pharmacology of YL-0919, a novel synthetic compound with combined high affinity and selectivity for serotonin transporter and 5-HT1A receptors. We performed in vitro binding and function assays and in vivo behavioral tests to assess the pharmacological properties and antidepressant-like efficacy of YL-0919. YL-0919 displayed high affinity in vitro to both 5-HT1A receptor and 5-HT transporter prepared from rat cortical tissue. It exerted an inhibitory effect on forskolin-stimulated cAMP formation and potently inhibited 5-HT uptake in both rat cortical synaptosomes and recombinant cells. After acute p.o. administration, very low doses of YL-0919 reduced the immobility time in tail suspension test and forced swimming test in mice and rats, with no significant effect on locomotor activity in open field test. Furthermore, WAY-100635 (a selective 5-HT1A receptor antagonist, 0.3 mg/kg) significantly blocked the effect of YL-0919 in tail suspension test and forced swimming test. In addition, chronic YL-0919 treatment significantly reversed the depressive-like behaviors in chronically stressed rats. These findings suggest that YL-0919, a novel structure compound, exerts dual effect on the serotonergic system, as both 5-HT1A receptor agonist and 5-HT uptake blocker, showing remarkable antidepressant effects in animal models. Therefore, YL-0919 may be used as a new option for the treatment of major depressive disorder.

Vilazodone: A landmark antidepressant approval or another “me-too” drug?

Vilazodone is a novel antidepressant which is indicated for the treatment of major depressive disorder (MDD) in adult patients. This article reviews the pharmacodynamics and pharmacokinetics of vilazodone, and discusses published and ongoing research on the medication.

Serotonin 5-HT1A receptors as targets for agents to treat psychiatric disorders: rationale and current status of research

Psychiatric disorders represent a large economic burden in modern societies. However, pharmacological treatments are still far from optimal. Drugs used in the treatment of major depressive disorder (MDD) and anxiety disorders (selective serotonin [5-HT] reuptake inhibitors [SSRIs] and serotonin-noradrenaline reuptake inhibitors [SNRIs]) are pharmacological refinements of first-generation tricyclic drugs, discovered by serendipity, and show low efficacy and slowness of onset. Moreover, antipsychotic drugs are partly effective in positive symptoms of schizophrenia, yet they poorly treat negative symptoms and cognitive deficits. The present article reviews the neurobiological basis of 5-HT1A receptor (5-HT1A-R) function and the role of pre- and postsynaptic 5-HT1A-Rs in the treatment of MDD, anxiety and psychotic disorders. The activation of postsynaptic 5-HT1A-Rs in corticolimbic areas appears beneficial for the therapeutic action of antidepressant drugs. However, presynaptic 5-HT1A-Rs play a detrimental role in MDD, since individuals with high density or function of presynaptic 5-HT1A-Rs are more susceptible to mood disorders and suicide, and respond poorly to antidepressant drugs. Moreover, the indirect activation of presynaptic 5-HT1A-Rs by SSRIs/SNRIs reduces 5-HT neuron activity and terminal 5-HT release, thus opposing the elevation of extracellular 5-HT produced by blockade of the serotonin transporter (SERT) in the forebrain. Chronic antidepressant treatment desensitizes presynaptic 5-HT1A-Rs, thus reducing the effectiveness of the 5-HT1A autoreceptor-mediated negative feedback. The prevention of this process by the non-selective partial agonist pindolol accelerates clinical antidepressant effects. Two new antidepressant drugs, vilazodone (marketed in the USA) and vortioxetine (in development) incorporate partial 5-HT1A-R agonist properties with SERT blockade. Several studies with transgenic mice have also established the respective role of pre- and postsynaptic 5-HT1A-Rs in MDD and anxiety. In agreement with pharmacological studies, presynaptic and postsynaptic 5-HT1A-R activation appears necessary for anxiolytic and antidepressant effects, respectively, yet, neurodevelopmental roles for 5-HT1A-Rs are also involved. Likewise, the use of small interference RNA has enabled the showing of robust antidepressant-like effects in mice after selective knock-down of 5-HT1A autoreceptors. Postsynaptic 5-HT1A-Rs in the prefrontal cortex (PFC) also appear important for the superior clinical effects of clozapine and other second-generation (atypical) antipsychotic drugs in the treatment of schizophrenia and related psychotic disorders. Despite showing a moderate in vitro affinity for 5-HT1A-Rs in binding assays, clozapine displays functional agonist properties at this receptor type in vivo. The stimulation of 5-HT1A-Rs in the PFC leads to the distal activation of the mesocortical pathway and to an increased dopamine release in PFC, an effect likely involved in the clinical actions of clozapine in negative symptoms and cognitive deficits in schizophrenia. The anxiolytic/antidepressant properties of 5-HT1A-R agonists in preclinical tests raised expectations enormously. However, these agents have achieved little clinical success, possibly due to their partial agonist character at postsynaptic 5-HT1A-Rs, together with full agonist properties at presynaptic 5-HT1A autoreceptors, as well as their gastrointestinal side effects. The partial 5-HT1A-R agonists buspirone, gepirone, and tandospirone are marketed as anxiolytic drugs, and buspirone is also used as an augmentation strategy in MDD. The development of new 5-HT1A-R agonists with selectivity for postsynaptic 5-HT1A-Rs may open new perspectives in the field.

New design strategies for antidepressant drugs

INTRODUCTION

In spite of research efforts spanning six decades, the most prominent antidepressant drugs to date still carry several adverse effects, often serious enough to warrant discontinuation of the drug. Molecular mechanisms of depression are now better understood such that some of the specific receptors responsible can be targeted for activation or inhibition. This advance, coupled with the recent availability of crystal structures of relevant drug targets or their homologs, has opened the door for new antidepressant therapeutic compounds.

AREAS COVERED

The authors review the evolution of monoamine-based antidepressant drugs, up to the selective serotonin reuptake inhibitors (SSRIs). The authors discuss classic and contemporary antidepressant drug design strategies, with a focus on virtual screening and fragment-based drug design methods. Furthermore, they discuss the recent advancements in the understanding of the serotonin transporter (SERT) structure/function relationship in the context of recognition of SSRIs and outline a strategy for the use of computational approaches in producing new SSRI lead compounds.

EXPERT OPINION

The authors suggest that given the long-awaited availability of credible three-dimensional structures for the SERT and related monoamine transporter proteins, cutting-edge computational methods should be the linchpin of future drug discovery efforts regarding monoamine-based antidepressant lead compounds. Because these transporter inhibitors cause a ubiquitous increase in extraneuronal neurotransmitter levels leading to side and adverse therapeutic effects, the drug discovery should extend to appropriate manipulation of the 'downstream' receptors affected by the neurotransmitter boost. Efficient use of new computational strategies will accelerate the drug discovery process and reduce its economic burden.

Monoamine neurocircuitry in depression and strategies for new treatments

Extensive studies showed that monoaminergic neurotransmission that involves serotonin (5-HT), norepinephrine (NE) and dopamine (DA) exerts major influence on brain circuits concerned by the regulation of mood, reactivity to psychological stress, self-control, motivation, drive, and cognitive performance. Antidepressants targeting monoamines directly affect the functional tone of these circuits, notably in limbic and frontocortical areas, and evidence has been provided that this action plays a key role in their therapeutic efficacy. Indeed, at least some of functional changes detected by functional magnetic resonance imaging in emotion- and cognitive-related circuits such as the one involving limbic-cortical-striatal-pallidal-thalamic connections in depressed patients can be reversed by monoamine-targeted antidepressants. However, antidepressants acting selectively on only one monoamine, such as selective inhibitors of 5-HT or NE reuptake, alleviate depression symptoms in a limited percentage of patients, and are poorly effective to prevent recurrence. Thorough investigations for the last 30 years allowed the demonstration of the existence of functional interactions between 5-HT, NE and DA systems, and the identification of the specific receptors involved. In particular, 5-HT systems were shown to exert negative influence on NE and DA systems through 5-HT2A and 5-HT2C receptor- mediated mechanisms, respectively. On the other hand, complex positive and negative influences of NE system on 5-HT neurotransmission are mediated through α1- and α2-adrenergic receptors, respectively. These data provided a rationale for the design of new, multimodal, therapeutic strategies involving drugs acting not only at the "historical" targets such as the 5-HT and/or the NE transporter, but also at other molecular targets to improve their efficacy and their tolerability.

Synthesis and biological evaluation of novel pyrrolidine-2,5-dione derivatives as potential antidepressant agents. Part 1

A series of 3-(1H-indol-3-yl)pyrrolidine-2,5-dione derivatives was synthesized and their biological activity was evaluated. The chemical structures of the newly prepared compounds were confirmed by (1)H NMR, (13)C NMR and ESI-HRMS spectra data. All tested compounds proved to be potent 5-HT1A receptor and serotonin transporter protein (SERT) ligands. Among them, compounds 15, 18, 19 and 30 showed significant affinity for 5-HT1A and SERT. Computer docking simulations carried out for compounds 15, 31 and 32 to models of 5-HT1A receptor and SERT confirm the results of biological tests. Due to high affinity for the 5-HT1A receptor and moderate affinity for SERT, compounds 31, 32, 35, and 37 were evaluated for their affinity for D2L, 5-HT6, 5-HT7 and 5-HT2A receptors. In vivo tests, in turn, resulted in determining the functional activity of compounds 15, 18, 19 and 30 to the 5-HT1A receptor. The results of these tests indicate that all of the ligands possess properties characteristic of 5-HT1A receptor agonists.

Future directions for serotonin and antidepressants

Despite the widespread use of antidepressant medications that block serotonin (5-hydroxytryptamine; 5-HT) and/or norepinephrine (NE) transporters, such as SSRIs (selective serotonin reuptake inhibitors) or SNRIs (serotonin and norepinephrine reuptake inhibitors), the underlying neurobiological basis of action of these agents is poorly understood. Increases in serotonergic function are hypothesized to have beneficial effects on depressive symptoms. However, which of the 14 different neuronal receptors sensitive to 5-HT accounts for the therapeutic effects of SSRIs and SNRIs remains undetermined. The development of drugs that activate or block specific 5-HT receptors may help to circumvent the two main limitations of current antidepressants: low efficacy and delayed onset of therapeutic action. What follows is a short summary of the author's views on this matter.

Vilazodone: a novel antidepressant

PURPOSE

The pharmacology and pharmacokinetics of the antidepressant vilazodone (approved for U.S. marketing in 2011) are reviewed, with an emphasis on efficacy and safety data from Phase III clinical trials.

SUMMARY

Vilazodone (marketed as Viibryd by Forest Pharmaceuticals) is a dual-acting serotonergic agent that combines the antidepressant effects of a selective serotonin-reuptake inhibitor (SSRI) with partial serotonin (5-HT)(1A)-receptor agonist activity. In two published eight-week Phase III trials involving a total of 878 adults with major depressive disorder (MDD), vilazodone use was found to yield significant symptomatic improvements relative to placebo use, as determined by mean changes from baseline in scores on the Hamilton Depression Rating Scale and other widely used clinical assessment instruments. Vilazodone hydrochloride therapy should be initiated at a dosage of 10 mg once daily and incrementally adjusted over 14 days to the recommended target daily dose of 40 mg; for optimal bioavailability and effectiveness, it should be taken after a light or high-fat meal. The adverse effects most commonly reported in clinical trials of vilazodone were diarrhea, nausea, vomiting, and insomnia.

CONCLUSION

Vilazodone is an efficacious and safe new antidepressant for the treatment of MDD. Its relatively high cost and adverse-effect profile, as well as a lack of data demonstrating that vilazodone can produce long-term MDD remission and offer significant advantages over the current standard of care, may limit the usefulness of vilazodone in clinical practice.