Electrophysiological characterization of the effects of asenapine at 5-HT(1A), 5-HT(2A), alpha(2)-adrenergic and D(2) receptors in the rat brain

Molecular basis of human trace amine-associated receptor 1 activation

The human trace amine-associated receptor 1 (hTAAR1, hTA1) is a key regulator of monoaminergic neurotransmission and the actions of psychostimulants. Despite preclinical research demonstrating its tractability as a drug target, its molecular mechanisms of activation remain unclear. Moreover, poorly understood pharmacological differences between rodent and human TA1 complicate the translation of findings from preclinical disease models into novel pharmacotherapies. To elucidate hTA1's mechanisms on the molecular scale and investigate the underpinnings of its divergent pharmacology from rodent orthologs, we herein report the structure of the human TA1 receptor in complex with a Gαs heterotrimer. Our structure reveals shared structural elements with other TAARs, as well as with its closest monoaminergic orthologue, the serotonin receptor 5-HT4R. We further find that a single mutation dramatically shifts the selectivity of hTA1 towards that of its rodent orthologues, and report on the effects of substituting residues to those found in serotonin and dopamine receptors. Strikingly, we also discover that the atypical antipsychotic medication and pan-monoaminergic antagonist asenapine potently and efficaciously activates hTA1. Together our studies provide detailed insight into hTA1 structure and function, contrast its molecular pharmacology with that of related receptors, and uncover off-target activities of monoaminergic drugs at hTA1.

Molecular Basis of Human Trace Amine-Associated Receptor 1 Activation

The human trace amine-associated receptor 1 (hTAAR1, hTA1) is a key regulator of monoaminergic neurotransmission and the actions of psychostimulants. Despite preclinical research demonstrating its tractability as a drug target, its molecular mechanisms of activation remain unclear. Moreover, poorly understood pharmacological differences between rodent and human TA1 complicate the translation of findings from preclinical disease models into novel pharmacotherapies. To elucidate hTA1's mechanisms on the molecular scale and investigate the underpinnings of its divergent pharmacology from rodent orthologs, we herein report the structure of the human TA1 receptor in complex with a Gαs heterotrimer. Our structure reveals shared structural elements with other TAARs, as well as with its closest monoaminergic ortholog, the serotonin receptor 5-HT4R. We further find that a single mutation dramatically shifts the selectivity of hTA1 towards that of its rodent orthologs, and report on the effects of substituting residues to those found in serotonin and dopamine receptors. Strikingly, we also discover that the atypical antipsychotic medication and pan-monoaminergic antagonist asenapine potently and efficaciously activates hTA1. Together our studies provide detailed insight into hTA1 structure and function, contrast its molecular pharmacology with that of related receptors, and uncover off-target activities of monoaminergic drugs at hTA1.

Agonistic properties of a series of psychotropic drugs at 5-HT1A receptors in rat and human brain membranes determined by [35S]GTPγS binding assay

BACKGROUND

Many psychoactive compounds have been developed to have more beneficial clinical efficacy than conventional drugs by adding agonistic action at 5-HT_1A receptors. The aim of the present study was to evaluate several psychotropic drugs that had been reported to behave as an agonist at 5-HT_1A receptor (aripiprazole, brexpiprazole, asenapine, lurasidone, and vortioxetine) in both rat and postmortem human brain membranes.

METHODS

The [³⁵S]GTPγS binding assay for G_i/o proteins coupled with 5-HT_1A receptors was performed in rat brain membranes and postmortem human brain membranes.

RESULTS

The specific binding was stimulated by brexpiprazole in rat hippocampus, human hippocampus, and human prefrontal cortex. Aripiprazole also behaved as an agonist in the same brain regions. Interestingly, its potency was much higher in rat hippocampal membranes than in human brain membranes, indicating the possibility of species differences. Although vortioxetine was an efficacious stimulator at high concentrations, its potency was undeterminable because of a lack of saturability. In addition to 5-HT_1A receptor agonism, involvement of other components, e.g., 5-HT_1B receptor agonism, was speculated by the biphasic inhibitory effects of the selective 5-HT_1A receptor neutral antagonist. Negligible stimulatory effects were obtained as to lurasidone and asenapine.

CONCLUSIONS

Our previous studies have raised the concept of a psychoactive drug group with a common pharmacological mechanism of action, i.e., 5-HT_1A receptor agonism, consisting of perospirone, aripiprazole, ziprasidone, clozapine, quetiapine, nemonapride, and trazodone. The present study demonstrates the data indicating that brexpiprazole and probably vortioxetine are included in this drug group. Lurasidone and asenapine are excluded from this group.

N,N-Dimethyltryptamine attenuates spreading depolarization and restrains neurodegeneration by sigma-1 receptor activation in the ischemic rat brain

Dimethyltryptamine (DMT), an endogenous ligand of sigma-1 receptors (Sig-1Rs), acts against systemic hypoxia, but whether DMT may prevent cerebral ischemic injury is unexplored. Here global forebrain ischemia was created in anesthetized rats and aggravated with the induction of spreading depolarizations (SDs) and subsequent short hypoxia before reperfusion. Drugs (DMT, the selective Sig-1R agonist PRE-084, the Sig-1R antagonist NE-100, or the serotonin receptor antagonist asenapine) were administered intravenously alone or in combination while physiological variables and local field potential from the cerebral cortex was recorded. Neuroprotection and the cellular localization of Sig-1R were evaluated with immunocytochemistry. Plasma and brain DMT content was measured by 2D-LC-HRMS/MS. The affinity of drugs for cerebral Sig-1R was evaluated with a radioligand binding assay. Both DMT and PRE-084 mitigated SDs, counteracted with NE-100. Further, DMT attenuated SD when co-administered with asenapine, compared to asenapine alone. DMT reduced the number of apoptotic and ferroptotic cells and supported astrocyte survival. The binding affinity of DMT to Sig-1R matched previously reported values. Sig-1Rs were associated with the perinuclear cytoplasm of neurons, astrocytes and microglia, and with glial processes. According to these data, DMT may be considered as adjuvant pharmacological therapy in the management of acute cerebral ischemia.

Recent advances in the development of asenapine formulations

INTRODUCTION

Asenapine maleate (AM) is an atypical antipsychotic agent, that has been widely prescribed for the management of schizoaffective disorders. However, the bioavailability of AM is extremely poor due to the extensive first-pass metabolism. With the advancement in pharmaceutical technologies, significant strides have been made to create novel formulations to address the bioavailability problem of AM.

AREAS COVERED

This review article provides an insight into all the formulation approaches undertaken by researchers to increase the bioavailability of AM encompassing the works utilizing ultrasound mediated transdermal delivery, nose to brain delivery, intestinal lymphatic system targeting, in situ implants, etc. All the patents associated with AM formulation have also been discussed and summarized.

EXPERT OPINION

Numerous studies have been carried out on AM formulations over the recent years, many of these studies have shown significant improvement in bioavailability. We have also mentioned the unexplored domains which can be exploited for further enhancing the bioavailability of AM. Nonetheless, most of these studies are still limited to the research laboratory level and face multiple hurdles before making into the market. Attaining controllability and reproducibility for the production of novel formulations is needed to enable its transition from bench to bedside.

Preparation, characterization, and optimization of asenapine maleate mucoadhesive nanoemulsion using Box-Behnken design: In vitro and in vivo studies for brain targeting

The tight junctions between capillary endothelial cells of the blood-brain barrier (BBB) restricts the entry of therapeutics into the brain. Potential of the intranasal delivery tool has been explored in administering the therapeutics directly to the brain, thus bypassing BBB. The objective of this study was to develop and optimize an intranasal mucoadhesive nanoemulsion (MNE) of asenapine maleate (ASP) in order to enhance the nasomucosal adhesion and direct brain targetability for improved efficacy and safety. Box-Behnken statistical design was used to recognize the crucial formulation variables influencing droplet size, size distribution and surface charge of ASP-NE. ASP-MNE was obtained by incorporating GRAS mucoadhesive polymer, Carbopol 971 in the optimized NE. Optimized ASP-MNE displayed spherical morphology with a droplet size of 21.2 ± 0.15 nm and 0.355 polydispersity index. Improved ex-vivo permeation was observed in ASP-NE and ASP-MNE, compared to the ASP-solution. Finally, the optimized formulation was found to be safe in ex-vivo ciliotoxicity study on sheep nasal mucosa. The single-dose pharmacokinetic study in male Wistar rats revealed a significant increase in concentration of ASP in the brain upon intranasal administration of ASP-MNE, with a maximum of 284.33 ± 5.5 ng/mL. The time required to reach maximum brain concentration (1 h) was reduced compared to intravenous administration of ASP-NE (3 h). Furthermore, it has been established during the course of present study, that the brain targeting capability of ASP via intranasal administration had enhanced drug-targeting efficiency and drug-targeting potential. In the animal behavioral studies, no extrapyramidal symptoms were observed after intranasal administration of ASP-MNE, while good locomotor activity and hind-limb retraction test established its antipsychotic activity in treated animals. Thus, it can be concluded that the developed intranasal ASP-MNE could be used as an effective and safe tool for brain targeting of ASP in the treatment of psychotic disorders.

Screening of nanoemulsion components for asenapine maleate using validated RP-HPLC method

A novel, simple reversed-phase high-performance liquid chromatographic (RP-HPLC) analytical method was developed and validated for the quantitative determination of asenapine from various nanoemulsion components during pre-formulation screening. The developed method was validated according to ICH Q2 (R1) guidelines. The developed and validated method was precisely and accurately quantified asenapine in various oils, surfactants and co-surfactants. The separation of asenapine was carried out on Hypersil BDS C18, 250×4.6mm, 5μm particle size column using methanol: acetonitrile (90:10) as mobile phase with a flow rate of 1mL.min^-1. Measurement at 270nm for the concentration range of 5 to 50μg.mL^-1 of the analyte was found to be linear with the determination coefficient (r²) of 0.999 as calculated by the least square regression method. The validated method was sensitive with LOD of 10.0ng.mL^-1 and LOQ of 30.0ng.mL^-1. Further, the method was precise and accurate, where the intraday and interday precision values were ranged from 0.70-0.95 and 0.36-0.95, respectively with the corresponding accuracy were ranged from 98.80-100.63 and 98.36-100.63. This developed and validated RP-HPLC method for asenapine was applied in the quantitative determination and screening of various oils, surfactants, and co-surfactants during the development of the asenapine maleate nanoemulsion.

Transdermal Asenapine in Schizophrenia: A Systematic Review

BACKGROUND

Asenapine is a novel antipsychotic that has demonstrated efficacy in controlling psychosis in schizophrenia and mania in bipolar illness. It must be administered as a sublingual formulation because it is nearly completely metabolized in the first pass through the liver. Recently, a transdermal formulation of asenapine has been approved for schizophrenia by the Food and Drug Administration.

METHODS

A systematic review of transdermal asenapine was done utilizing the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) model.

DISCUSSION

There are several formulations of transdermal asenapine but only Secuado^® has been approved for clinical use. Total bioavailability is 35%. Peak plasma concentration (Cmax) is 4 ng/mL and occurs within 1 hr (Tmax); elimination half-life (t_1/2) is 24 hrs (range 13.4 to 39.2 h). Asenapine is highly bound (95%) to albumin and α₁-acid glycoprotein. It has a unique receptor profile in which it functions as an antagonist at multiple receptors with affinity that is higher than D₂ (K_i = 1.3) including D₃, D₄, 5HT_2A, 5HT_2C, 5HT_2B, 5HT₇, 5HT₆, H₁, and α2. This profile suggests that asenapine may be of particular value off label for bipolar depression, anxiety, and aggression. Transdermal asenapine was only tested in one randomized, placebo-controlled study of acute psychosis in schizophrenia. It was superior to placebo at week 6 with nearly one-third of patients experiencing >30% improvement in total PANSS score which translates in a number needed to treat (NNT) of 9.

Asenapine for the treatment of bipolar disorder

Introduction: Bipolar I disorder (BDI) is amongst the most debilitating psychiatric conditions with a great impact on both patients and their families. A class of drugs commonly used in this condition is second-generation antipsychotics (SGAs) including asenapine, one of the latest to be introduced into the clinical practice worldwide to treat manic episodes in BDI. Areas covered: The aim of this paper is to critically review the literature on the pharmacological characteristics, tolerability, and safety data of asenapine, as well as on its short- and long-term clinical trials in manic episodes as both a monotherapy and as an add-on treatment. Expert opinion: The available data indicate that asenapine is an effective antimanic agent in both adult and pediatric patients and that it might also improve depressive symptoms and recurrences in BDI patients. Its tolerability profile is good, and its most common side effects are somnolence, light extrapyramidal symptoms, dizziness, weight gain, and oral (but reversible) hypoesthesia. Taken together, the published studies indicate that asenapine might be an effective therapeutic agent in BDI with a broad spectrum of clinical activities. Further double-blind, short- and long-term studies are, however, necessary to clarify its precise role in the treatment of BD.

Involvement of 5-HT1A and 5-HT2A Receptors but Not α 2-Adrenoceptors in the Acute Electrophysiological Effects of Cariprazine in the Rat Brain In Vivo

Cariprazine, an orally active and potent dopamine D₃-preferring D₃/D₂ receptor partial agonist, is approved to treat adults with schizophrenia (in the United States and Europe) and manic or mixed episodes associated with bipolar I disorder (in the United States). Cariprazine also displays partial agonism at serotonin [5-hydroxytryptamine (5-HT)] 5-HT_1A receptors and antagonism at 5-HT_2A and 5-HT_2B receptors in vitro. The study objective was to determine whether cariprazine leads to functional alterations of monoamine systems in vivo via electrophysiological recordings from anesthetized rats. Dorsal raphe nucleus (DRN), locus coeruleus (LC), and hippocampus pyramidal neurons were recorded, and cariprazine was administered systemically or locally through iontophoresis. In the DRN, cariprazine completely inhibited the firing activity of 5-HT neurons, which was fully reversed by the 5-HT_1A receptor antagonist, WAY100635. In the LC, cariprazine reversed the inhibitory effect of the preferential 5-HT_2A receptor agonist, 2,5-dimethoxy-4-iodoamphetamine, on norepinephrine (NE) neurons (ED₅₀ = 66 µg/kg) but did not block the inhibitory effect of the α ₂-adrenergic receptor agonist, clonidine. Cariprazine, iontophorized into the hippocampus, diminished pyramidal neuronal firing through activation of 5-HT_1A receptors, while its concomitant administration did not dampen the suppressant effect of 5-HT. These results indicate that, in vivo, cariprazine acted as a 5-HT_1A autoreceptor agonist in the DRN, a 5-HT_2A receptor antagonist in modulating the firing activity of LC NE neurons, and a full agonist at 5-HT_1A receptors mediating the electrophysiological effect of 5-HT on pyramidal neurons. The modulatory actions of cariprazine on these monoaminergic systems may contribute to its therapeutic effectiveness in patients with depressive episodes.

A Review of Asenapine in the Treatment of Bipolar Disorder

Bipolar disorder places a significant burden on the affected individuals, their family, healthcare systems and the overall economy. More treatment options are needed, especially those with better efficacy and tolerability. Asenapine is a second-generation antipsychotic approved in Europe (brand name Sycrest^®) for the treatment of moderate-to-severe manic episodes associated with bipolar I disorder in adults, and in the US (brand name Saphris^®) for the treatment of manic or mixed episodes of bipolar I disorder in adults and children aged 10-17 years. It is the antagonistic activity at the D₂ receptor that is likely responsible for the antimanic properties of asenapine. Clinical trials have demonstrated that asenapine mono- and add-on therapy is effective in the short- and long-term treatment of mania associated with bipolar I disorder in adult and paediatric patients. In addition, post hoc and pooled data analyses have shown that asenapine is effective in reducing clinically significant depressive symptoms in patients with bipolar I disorder. The most common adverse events associated with asenapine are somnolence, dizziness, extrapyramidal symptoms, increased bodyweight and oral hypoesthesia. However, the incidence of these events, particularly weight gain, is generally lower than with olanzapine. In one study, asenapine has been shown to improve health-related quality of life. Economic analyses indicate that the use of asenapine can, over time, lead to a reduction in the costs of treatment.

Asenapine modulates mood-related behaviors and 5-HT1A/7 receptors-mediated neurotransmission

AIM

Asenapine is a new atypical antipsychotic prescribed for the treatment of psychosis/bipolar disorders that presents higher affinity for serotonergic than dopaminergic receptors. The objective of this study was to investigate its antidepressant-like and antimanic-like properties on relevant animal models of depression and mania and to assess the acute and chronic effect of Asenapine on dorsal raphe nucleus (DRN) 5-HT cell firing activity.

METHODS

We assessed the effects of Asenapine using in vivo electrophysiological and behavioral assays in rats.

RESULTS

Behavioral experiments showed that Asenapine had no significant effect on immobility time in the forced swim test (FST) in control rats. In the ACTH-treated rats, a model of antidepressant-resistance, Asenapine failed to alter immobility time in the FST. In contrast in the sleep deprivation (SD) model of mania, acute administration of Asenapine significantly decreased the hyperlocomotion of SD rats. In the DRN, acute administration of Asenapine reduced the suppressant effect of the selective 5-HT₇ receptor agonist LP-44 and of the prototypical 5-HT_1A receptor agonist 8-OH-DPAT on 5-HT neuronal firing activity. In addition, chronic treatment with Asenapine enhanced DRN 5-HT neuronal firing and this effect was associated with an alteration of the 5-HT₇ receptor responsiveness.

CONCLUSION

These results confirm that Asenapine displays robust antimanic property and effective in vivo antagonistic activity at 5-HT_1A/7 receptors.

Asenapine reduces anxiety-related behaviours in rat conditioned fear stress model

OBJECTIVE

Asenapine is an atypical antipsychotic that is currently available for the treatment of schizophrenia and bipolar I disorder. Although the atypical antipsychotics clozapine and olanzapine are effective for depression and anxiety in schizophrenia, as demonstrated by animal model studies, this has not been clarified for asenapine. Therefore, we compared the effects of asenapine in the conditioned fear stress model with those of clozapine and olanzapine.

METHOD

Rats were individually fear conditioned using electrical foot shock in a Skinner box. Approximately 24 h later, individual animals were returned to the same Skinner box (without electrical shock) and their freezing behaviour was observed for 5 min. Animals were treated with asenapine, clozapine, olanzapine, the 5-HT1A receptor partial agonist buspirone, or the 5-HT2C receptor antagonist SB242084 at 30 min before freezing behaviour assessment. The 5-HT1A receptor antagonist WAY100635 or the 5-HT2C receptor agonist Ro60-0175 was also used concomitantly with asenapine. The effects of asenapine, clozapine, and olanzapine on serotonin release in the rat hippocampus were also measured using in vivo microdialysis.

RESULTS

Asenapine reduced freezing behaviour, while neither clozapine nor olanzapine reduced freezing behaviour. Buspirone and SB242084 also reduced freezing behaviour. The effect of asenapine in reducing freezing behaviour was not altered by the concomitant administration of WAY100635 or Ro60-0175. Both asenapine and clozapine, but not olanzapine, increased serotonin release in the rat hippocampus.

CONCLUSION

Asenapine may have superior therapeutic effect on anxiety symptoms than other agents, although the underlying mechanism of its anxiolytic activity remains unknown.

Management of depressive symptoms in schizophrenia

BACKGROUND

Although depressive symptoms are a frequently occurring phenomenon in schizophrenia, effective treatments remain an area of clinical need.

OBJECTIVE

To assess the benefit of short-term treatment with the atypical antipsychotic asenapine versus placebo on depressive symptoms in patients with acute schizophrenia in an exacerbated state.

METHODS

Data were pooled from intent-to-treat (ITT) populations of three 6-week, randomized controlled studies with fixed doses of asenapine (ASE; n=427), olanzapine (OLA; n=82), risperidone (RIS; n=54), haloperidol (HAL; n=97), or placebo (PLA; n=254). Change from baseline Calgary Depression Scale for Schizophrenia (CDSS) total score and individual item scores were assessed at Day 21 and Day 42 in the total patient population (n=914), and in patients presenting with a CDSS total score of .6 at baseline (n=248). Mixed model repeated measures (MMRM) analyses were performed on patient data.

RESULTS

The observed change from baseline in CDSS total score was significantly larger with ASE.compared to PLA.at both Day 21 (p<0.05) and Day 42 (p<0.01) for the total patient population group, and at Day 21 (p<0.05) in patients with baseline CDSS total score .6. For both populations, there was a significant change from baseline in the CDSS depression item score with ASE.compared to PLA.at Day 21 (p<0.01, all patient population; p<0.05, patients with baseline CDSS .6), and at Day 42 (p<0.01) in the all patient population. Statistically significant changes from baseline, in favor of ASE versus PLA, were also observed in other individual CDSS item scores including hopelessness (p<0.05, Day 21, patients with baseline CDSS .6), self-depreciation (p<0.05, Day 42, all patient population), guilty ideas of reference (p<0.01, Day 42, all patient population), pathological guilt (p<0.01, Day 21, all patient population; p<0.05, Day 21 and Day 42, patients with baseline CDSS score .6), and observed depression (p<0.05, Day 21, all patient population).

CONCLUSIONS

ASE significantly improved a range of depressive symptoms in people with an acute exacerbation of schizophrenia, as measured by the CDSS. ASE may represent a beneficial treatment option for the management of depressive symptoms in patients with schizophrenia.

Brexpiprazole Alters Monoaminergic Systems following Repeated Administration: an in Vivo Electrophysiological Study

BACKGROUND

Brexpiprazole was recently approved as adjunctive therapy for depression and treatment of schizophrenia in adults. To complement results from a previous study in which its acute effects were characterized, the present study assessed the effect of repeated brexpiprazole administration on monoaminergic systems.

METHODS

Brexpiprazole (1mg/kg, subcutaneous) or vehicle was administered once daily for 2 and 14 days. Single-unit electrophysiological recordings from noradrenaline neurons in the locus coeruleus, serotonin neurons in the dorsal raphe nucleus, dopaminergic neurons in the ventral tegmental area, and pyramidal neurons in the hippocampus CA3 region were obtained in adult male Sprague-Dawley rats under chloral hydrate anesthesia within 4 hours after final dosing.

RESULTS

Brexpiprazole blunted D2 autoreceptor responsiveness, while firing activity of ventral tegmental area dopaminergic neurons remained unaltered. Brexpiprazole increased the firing rate of locus coeruleus noradrenaline neurons and increased noradrenaline tone on α2-adrenergic receptors in the hippocampus. Administration of brexpiprazole for 2 but not 14 days increased the firing rate of serotonin neurons in the dorsal raphe nucleus. In the hippocampus, serotonin1A receptor blockade significantly disinhibited pyramidal neurons after 2- and 14-day brexpiprazole administration. In contrast, no significant disinhibition occurred after 24-hour washout or acute brexpiprazole.

CONCLUSIONS

Repeated brexpiprazole administration resulted in a marked occupancy of D2 autoreceptors, while discharge activity of ventral tegmental area dopaminergic neurons remained unaltered. Brexpiprazole enhanced serotonergic and noradrenergic tone in the hippocampus, effects common to antidepressant agents. Together, these results provide further insight in the neural mechanisms by which brexpiprazole exerts antidepressant and antipsychotic effects.

Asenapine in the Treatment of Acute Mania: A Real-World Observational Study With 6 Months Follow-Up

Asenapine is a second-generation antipsychotic with a unique pharmacological profile that was recently approved for the treatment of moderate/severe manic episodes. Real-world data on rapidity of action in inpatient settings are lacking.The aims of the current real-world observational study were to evaluate: (i) short-term efficacy of asenapine after 7 days (T0-T1) in patients hospitalized for a manic episode in the course of bipolar I disorder or schizoaffective disorder (group A), (ii) differences in length of stay (LoS), and (iii) rehospitalization compared to a control population (group B) with a 6-month follow-up.Twenty patients were included in each group. The mean total Young Mania Rating Scale score decreased by 12.6 (SD ±10.3; t(17) = 5.2, P < 0.005), implying a mean 37.8% improvement. A statistically significant reduction was observed for all Young Mania Rating Scale items, except for "sexual interest." The mean total BPRS score decreased by 17.2 (SD ±14.9; t(17) = 4.9, P < 0.005). A statistically significant reduction was observed for several items, including "conceptual disorganization," "grandiosity," "unusual thought content," and "excitement". Length of stay was 17.9 (SD ±9.0) days for group A and 14.7 (SD ±12.7) days for group B; the result of the Kruskal-Wallis test showed no significant differences (χ = 2.199, P = 0.138). Despite a high discontinuation rate, only 17.7% of patients in group A were rehospitalized in the following 6 months compared to 41.2% of those in group B (relative risk = 0.43, 95% confidence interval, 0.13-1.39).Findings from this small, preliminary study at least partially support the results of previous trials, confirming effectiveness and tolerability in the context of comorbidity and polypsychopharmacology.

Asenapine alters the activity of monoaminergic systems following its subacute and long-term administration: an in vivo electrophysiological characterization

Asenapine is a tetracyclic atypical antipsychotic used for treatment of schizophrenia and mania. Previous in vivo electrophysiological studies demonstrated antagonistic action of asenapine at dopamine D2, serotonin (5-HT)2A, and α2-adrenergic receptors. Here, we assessed monoamine system activities after two-day and 21-day asenapine administration at a dosage (0.1mg/kg/day) resulting in clinically relevant plasma levels. In the ventral tegmental area (VTA), asenapine increased the number of spontaneously active dopamine neurons, while firing parameters remained unchanged. Asenapine partially prevented the D2 autoreceptor-mediated inhibitory response to apomorphine after two days of administration. This effect was lost after 21 days of administration, suggesting adaptive changes leading to D2 receptor sensitization. Asenapine increased the firing activity of noradrenergic neurons in the locus coeruleus (LC) after 21, but not two days of administration. Furthermore, it potently blocked 5-HT2A receptors while α2-adrenergic receptors were unaffected by this drug regimen. Both acute and long-term asenapine administration partially blocked α2-adrenergic receptors in the CA3 region of the hippocampus, and noradrenergic tone on α1- and α2-adrenoceptors remained unchanged. In the dorsal raphe nucleus, asenapine increased the firing rate of 5-HT neurons after two, but not 21 days of administration. In addition, responsiveness of 5-HT1A autoreceptors was unaltered by asenapine. In the hippocampus, 21-day asenapine administration increased serotonergic tone by partial agonistic action on postsynaptic 5-HT1A and terminal 5-HT1B receptors. Taken together, asenapine had profound effects on both catecholamine systems, potently blocked 5-HT2A receptors, and enhanced 5-HT tone, effects that could be important in treatment of mood disorders and schizophrenia.

Adjunctive treatment with asenapine augments the escitalopram-induced effects on monoaminergic outflow and glutamatergic neurotransmission in the medial prefrontal cortex of the rat

BACKGROUND

Substantial clinical data support the addition of low doses of atypical antipsychotic drugs to selective serotonin reuptake inhibitors (SSRIs) to rapidly enhance the antidepressant effect in treatment-resistant depression. Preclinical studies suggest that this effect is at least partly explained by an increased catecholamine outflow in the medial prefrontal cortex (mPFC).

METHODS

In the present study we used in vivo microdialysis in freely moving rats and in vitro intracellular recordings of pyramidal cells of the rat mPFC to investigate the effects of adding the novel atypical antipsychotic drug asenapine to the SSRI escitalopram with regards to monoamine outflow in the mPFC and dopamine outflow in nucleus accumbens as well as glutamatergic transmission in the mPFC.

RESULTS

The present study shows that addition of low doses (0.05 and 0.1 mg/kg) of asenapine to escitalopram (5 mg/kg) markedly enhances dopamine, noradrenaline, and serotonin release in the rat mPFC as well as dopamine release in the nucleus accumbens. Moreover, this drug combination facilitated both N-methyl-d-Aspartate (NMDA)- and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-induced currents as well as electrically evoked excitatory postsynaptic potentials in pyramidal cells of the rat mPFC.

CONCLUSIONS

Our results support the notion that the augmentation of SSRIs by atypical antipsychotic drugs in treatment-resistant depression may, at least in part, be related to enhanced catecholamine output in the prefrontal cortex and that asenapine may be clinically used to achieve this end. In particular, the subsequent activation of the D1 receptor may be of importance for the augmented antidepressant effect, as this mechanism facilitated both NMDA and AMPA receptor-mediated transmission in the mPFC. Our novel observation that the drug combination, like ketamine, facilitates glutamatergic transmission in the mPFC may contribute to explain the rapid and potent antidepressant effect obtained when atypical antipsychotic drugs are added to SSRIs.

Asenapine, iloperidone and lurasidone: critical appraisal of the most recently approved pharmacotherapies for schizophrenia in adults

This article reviews the pharmacological profile and published efficacy and tolerability/safety data of iloperidone, asenapine and lurasidone, the most recent atypical antipsychotics to be approved in the USA for the treatment of schizophrenia. All three agents are similar in terms of overall efficacy and low propensity for clinically significant weight gain or adverse changes in glycemic or lipid profile. However, these agents differ from one another in terms of formulations, pharmacokinetics, and dosing and nonmetabolic adverse effect profile. For each drug, comparative and real-world effectiveness studies are lacking, as are effectiveness and safety data in elderly, young and pregnant/nursing patients. As such, the exact place of iloperidone, asenapine and lurasidone within the broader antipsychotic armamentarium is currently difficult to establish.

Asenapine for the treatment of manic and mixed episodes associated with bipolar I disorder: from clinical research to clinical practice

INTRODUCTION

Asenapine is a sublingually administered second-generation antipsychotic with proven efficacy for the treatment of moderate to severe manic episodes associated with bipolar I disorder in adults. Its relatively favorable weight and metabolic profile, as well as the lack of appreciable activity at muscarinic cholinergic receptors and the sublingual administration are of clinical interest.

AREAS COVERED

This paper comprises a review and commentary regarding the use of sublingual asenapine in the treatment of acute manic and mixed episodes of bipolar disorder. Basic principles in dosing, switching, management of side effects and co-administration with other medications are provided.

EXPERT OPINION

Asenapine displays quick and reliable effects on manic symptoms, very low risk of depressive switches, efficacy on depressive symptoms during manic and mixed episodes, usually good tolerability and continued longer-term efficacy on residual and subthreshold symptoms. The fast-dissolving sublingual route of administration may favor those who have difficulties in swallowing medications. Also, the sublingual administration reduces the risk of overdose when more than the prescribed tablets are swallowed. The relatively low metabolic risk and the lack of anticholinergic side effects contribute to making this medication a useful tool for the treatment of patients with bipolar disorder.

A framework to avoid irrational polypharmacy in psychiatry

Many patients with psychiatric disorders do not obtain remission from available pharmacological and psychotherapeutic treatments. Recent studies have demonstrated that there is a role for the rational use of 'combination therapy' when treating patients with serious and treatment-resistant mental illnesses. When prescribing multiple medications, it is easy, however, to fall into irrational polypharmacy. We present a framework that clinicians can use to avoid the pitfall of irrational polypharmacy. When using combination therapy, clinicians should consider: (a) pharmadynamic redundancy; (b) pharmacodynamic interactions; (c) pharmacokinetic interactions; and (d) avoid inadequate dosing of medications. Clinicians should also (e) regularly reassess the need for and benefit of continued combination therapy.

Iloperidone, asenapine and lurasidone: a primer on their current status

INTRODUCTION

Three newer atypical antipsychotic drugs were FDA-approved in 2009 and 2010 in the following order: iloperidone, asenapine and lurasidone. The three drugs are indicated for the treatment of acute schizophrenia. Asenapine is also approved for treatment of manic or mixed episodes associated with bipolar I disorder, for the maintenance treatment of schizophrenia and as an adjunctive therapy with lithium or valproate for the acute treatment of manic or mixed episodes associated with bipolar I disorder in adults.

AREAS COVERED

This review compares and contrasts the current preclinical, clinical, safety and tolerability profiles of the three newer drugs, as reported in published preclinical and clinical studies, product labels, poster presentations and press releases.

EXPERT OPINION

Preclinical studies have reported that the three drugs have variable affinities for a wide range of neurotransmitter receptors, and are active in animal models predictive of antipsychotic activity. Asenapine is the first antipsychotic to be administered sublingually, whereas iloperidone requires titration to minimize orthostatic hypotension. Asenapine and lurasidone are associated with dose-related akathisia, whereas iloperidone is not. The three drugs appear to have relatively benign metabolic profiles. The availability of the three novel antipsychotics should provide additional options for improved treatment of schizophrenia and other psychotic disorders.

Asenapine: a clinical review of a second-generation antipsychotic

BACKGROUND

Schizophrenia and bipolar disorder are both prevalent types of psychiatric illness in the United States. As second-generation antipsychotics have become a more viable first-line treatment option, their use has been associated with a new era of adverse events (AEs), most notably metabolic and cardiovascular concerns. Although treatment options for schizophrenia and bipolar disorder have arguably improved, there continues to be a need for medications that achieve and maintain desired efficacy with minimal AEs.

OBJECTIVES

This article serves as a comprehensive review of the pharmacologic profile of the second-generation antipsychotic asenapine, as well as a review of its efficacy and safety profiles based on the findings from clinical trials in schizophrenia and bipolar disorder.

METHODS

Searches of Ovid MEDLINE, EMBASE, and IDIS were conducted (January 1996 to November 2011) to identify clinical studies and other primary literature sources with the following search terms: asenapine, bipolar disorder, antipsychotic, psychosis, dopamine, and schizophrenia. Only studies of asenapine and placebo and/or active-comparator arms were included.

RESULTS

The literature search yielded 67 unique articles, including review articles, which were excluded. The efficacy of asenapine was reported in 3 clinical studies in patients with schizophrenia, 1 each in acute and long-term settings, measured as significant changes in Positive and Negative Syndrome Scale scores over 6 and 52 weeks. Asenapine also had reported efficacy in the prevention of relapse in schizophrenia during a 26-week extension study. In addition, efficacy of asenapine was reported in 2 studies in acute mania as well as extension phases of both 9 and 40 weeks, as determined by significant changes in Young Mania Rating Scale scores. The most commonly reported AEs in these studies were somnolence (13%-24%), extrapyramidal symptoms (EPS) (7%-12%), and dizziness (11%).

CONCLUSIONS

The findings from multiple studies have suggested that asenapine is efficacious in the acute treatment of schizophrenia. Asenapine has reported long-term efficacy for this indication and the potential to reduce the incidence of relapse. Asenapine efficacy was also reported in the treatment of acute manic or mixed states associated with bipolar I disorder. Asenapine had an acceptable safety profile across the different disease states studied, although it was not devoid of metabolic and EPS-related AEs.

Asenapine: a synthesis of efficacy data in bipolar mania and schizophrenia

INTRODUCTION

This article briefly reviews the efficacy, as well as safety and tolerability, data pertaining to asenapine in bipolar mania and schizophrenia. Postulated mechanism of action is also reviewed.

METHODS

A PubMed search was conducted using the search term asenapine. All displayed articles were reviewed; we selected for review studies that were part of the regulatory registration package to the FDA as part of the bipolar disorder and schizophrenia indication. We also included a review of articles reporting on asenapine's preclinical profile.

RESULTS

Asenapine is a recently introduced atypical antipsychotic approved by the FDA for bipolar mania and mixed states with or without psychotic features, as well as for the treatment and prevention of psychotic relapses in schizophrenia. Preliminary evidence suggests that asenapine mitigates depressive symptoms in bipolar mania and offers superior efficacy to olanzapine or risperidone in the negative symptoms of schizophrenia. The pharmacodynamic profile of asenapine provides a rationale for hypothesizing efficacy in the treatment of cognitive deficits in mood and psychotic disorders. Asenapine is associated with sedation and/or somnolence; it has a lower propensity to weight gain and metabolic disruption than olanzapine. Extrapyramidal side effects (EPS) are associated with asenapine and may be dose-dependent. Asenapine is not associated with sustained hyperprolactinemia or cardiovascular toxicity. Dysgeusia and oral hypoesthesia/paresthesia is associated with asenapine, but is rarely a cause for treatment discontinuation.

CONCLUSIONS

Asenapine is the only atypical antipsychotic available exclusively as a sublingual, fast-dissolved formulation. Electrophysiological, behavioral, pharmacological, and radioligand studies are predictive of antidepressant, mood-stabilizing, as well as antipsychotic, effects.

Review of pharmacological treatment in mood disorders and future directions for drug development

After a series of serendipitous discoveries of pharmacological treatments for mania and depression several decades ago, relatively little progress has been made for novel hypothesis-driven drug development in mood disorders. Multifactorial etiologies of, and lack of a full understanding of, the core neurobiology of these conditions clearly have contributed to these development challenges. There are, however, relatively novel targets that have raised opportunities for progress in the field, such as glutamate and cholinergic receptor modulators, circadian regulators, and enzyme inhibitors, for alternative treatment. This review will discuss these promising new treatments in mood disorders, the underlying mechanisms of action, and critical issues of their clinical application. For these new treatments to be successful in clinical practice, it is also important to design innovative clinical trials that identify the specific actions of new drugs, and, ideally, to develop biomarkers for monitoring individualized treatment response. It is predicted that future drug development will identify new agents targeting the molecular mechanisms involved in the pathophysiology of mood disorders.

Receptor mechanisms of antipsychotic drug action in bipolar disorder - focus on asenapine

The atypical antipsychotic drugs are considered a first-line treatment for mania in bipolar disorder with many having a proven superiority to the classical mood stabilisers. This review addresses the pharmacological mechanisms underlying this therapeutic efficacy, as well as those mechanisms considered responsible for the adverse effects of antipsychotic drugs, with a particular focus on the recently introduced asenapine. The high efficacy in bipolar mania of haloperidol, a relatively selective dopamine D2-like receptor antagonist, indicates that the one common receptor mechanism underlying antipsychotic effects on mania is antagonism at the D2 receptor. Serotonin receptors are implicated in antidepressant response, and relief of depressed mood in mixed states is likely to involve drug effects at one, or more likely several interacting, serotonin receptors. Asenapine shows a unique breadth of action at these sites, with potential effects at clinical doses at 5HT1A, 1B, 2A, 2C, 6 and 7 receptors. Antagonism at alpha2 adrenoceptors may also be involved. Adverse effects include those classically associated with dopamine D2 receptor blockade, the extrapyramidal side effects (EPS), and which are relatively diminished in the atypical (in comparison with the conventional) antipsychotics. A variety of protective mechanisms against EPS associated with different drugs include low D2 affinity, D2 partial agonism, high 5-HT2A and 2C antagonism. Similar effects at the D2 and 5-HT2C receptors may underlie the low propensity for hyperprolactinaemia of the atypicals, although the strong prolactin-elevating effect of risperidone reflects its relatively high blood/brain concentration ratio, a consequence of it being a substrate for the p-glycoprotein pump. Weight gain is a further concern of antipsychotic treatment of bipolar disorder which is particularly severe with olanzapine. Histamine H1, alpha1 adrenergic and particularly 5-HT2C receptors are implicated in this effect, although the lower propensity for weight gain shown by asenapine which, like olanzapine, binds to these receptors, indicates that other protective receptor mechanisms, or subtle differences in the 5-HT2C receptor-mediated effects, may be important. Of other peripheral and central effects, the pharmacological basis of sedation (H1 receptors) and postural hypotension (alpha1 adrenoceptors) are rather better understood. The relative benefits of atypical antipsychotics like asenapine can be understood from their receptor pharmacology, and this understanding is key to the future development of improved treatment for bipolar disorder.

Attenuation of chronic mild stress-induced 'anhedonia' by asenapine is not associated with a 'hedonic' profile in intracranial self-stimulation

Chronic mild stress (CMS)-induced 'anhedonia' is a predictive model of antidepressant activity. We assessed the reversal of CMS-induced behavioral changes by asenapine, the antidepressant imipramine, and the atypical antipsychotics olanzapine and risperidone. Secondarily, the ability of these agents to facilitate intracranial self-stimulation (ICSS) was assessed to ensure that any attenuation of CMS-induced anhedonia was not associated with an overt hedonic profile. After 2 weeks of CMS, male Wistar rats were administered asenapine (0.06-0.6 mg/kg), olanzapine (2 mg/kg), risperidone (0.5 mg/kg), or imipramine (10 mg/kg) by intraperitoneal injection over 5 weeks to examine their ability to reverse CMS-induced reductions in the intake of a sucrose solution. For the ICSS study, rats were trained to deliver an electrical stimulus to the ventral tegmental area. The effects of acute doses of subcutaneous asenapine (0.01-0.3 mg/kg), olanzapine (0.3 and 1 mg/kg), risperidone (0.1 and 0.3 mg/kg), and intraperitoneal imipramine (3-30 mg/kg), cocaine (5.0 mg/kg), or amphetamine (1.0 mg/kg) on ICSS were then examined. CMS significantly reduced sucrose intake (P < 0.001). All active agents (0.6 mg/kg asenapine, 2 mg/kg olanzapine, 0.5 mg/kg risperidone, and 10 mg/kg imipramine) reversed the effect of CMS (all P < 0.001). In the ICSS protocol, asenapine (0.01 and 0.03 mg/kg), olanzapine (1 mg/kg), and risperidone (0.3 mg/kg) impaired ICSS performance, whereas positive controls (5 mg/kg cocaine, 1 mg/kg amphetamine) facilitated ICSS. Asenapine reversed CMS-induced anhedonia without facilitating ICSS, providing support for a role of asenapine in treating bipolar disorder and aspects of negative and/or affective symptoms in schizophrenia.

Asenapine improves phencyclidine-induced object recognition deficits in the rat: evidence for engagement of a dopamine D1 receptor mechanism

RATIONALE

Cognitive deficits are common in schizophrenia. Asenapine is an atypical antipsychotic approved by the US Food and Drug Administration in adults for treatment of schizophrenia or acute treatment, as monotherapy or adjunct therapy to lithium or valproate, of manic or mixed episodes of bipolar I disorder.

OBJECTIVES

Based on the receptor pharmacology of asenapine, the current study assessed the efficacy and mechanism of action of asenapine to improve a subchronic phencyclidine (PCP)-induced deficit in visual recognition memory using the novel object recognition (NOR) paradigm in the rat, a paradigm of relevance to cognition in schizophrenia.

METHODS

Female-hooded Lister rats received vehicle or PCP (2 mg/kg, i.p.) for 7 days, followed by a 7-day washout. On the test day, rats were given asenapine (0.001-0.1 mg/kg, s.c.) alone or in combination with the D(1) receptor antagonist SCH-23390 (0.05 mg/kg, i.p.) or 5-HT(1A) receptor antagonist WAY100635 (1 mg/kg, i.p.). Time spent exploring two identical objects during a 3-min acquisition trial (followed by a 1-min intertrial interval) and then a familiar and a novel object for another 3 min (retention trial) were recorded onto videotape and scored blind.

RESULTS

In the retention trial, vehicle- but not PCP-treated animals explored the novel object significantly more than the familiar object (p < 0.001). Asenapine (0.01-0.075 mg/kg) reversed PCP-induced deficits in NOR (p < 0.01-0.001) in a dose-related manner. This effect was antagonised by SCH-23390 but not by WAY100635.

CONCLUSIONS

These results demonstrate a role for D(1) but not 5-HT(1A) receptor mechanisms in mediating the cognitive effects of asenapine in this rodent model.

Asenapine: a review of its use in the management of mania in adults with bipolar I disorder

Asenapine is an atypical antipsychotic agent available in sublingual formulations (5 or 10 mg) and indicated in the US (Saphris) for the acute treatment, as monotherapy or adjunctive therapy, of manic and mixed episodes and in the EU (Sycrest) for the treatment of moderate to severe manic episodes, in adult patients with bipolar I disorder. In two large (both n = 480), well designed, 3-week trials in adult patients with bipolar I disorder, asenapine monotherapy was significantly more effective than placebo at improving mania symptoms, as assessed using the Young Mania Rating Scale total score (YMRS; primary endpoint), with significant differences between the asenapine and placebo groups occurring after 2 days of treatment. In both trials, Clinical Global Impression for Bipolar Disorder (CGI-BP) scale mania severity scores exceeded those of placebo. In one trial, response and remission rates exceeded those of placebo. In a 9-week extension study that recruited completers from the monotherapy trials, there were no significant differences between asenapine and olanzapine groups in terms in Montgomery-Åsberg Depression Rating Scale (MADRS) scores, CGI-BP mania severity scores, YMRS response rates or YMRS remission rates during the extension phase. In the extension study, the efficacy of asenapine monotherapy appeared to be maintained over 40 weeks (total treatment duration of 52 weeks). In a 12-week trial of asenapine as adjunctive therapy to lithium or valproate, asenapine was more effective than placebo in improving manic symptoms, based on the difference between groups in the YMRS total score at week 3 (primary endpoint). Most adverse events associated with asenapine were of mild to moderate severity, with <7% of asenapine recipients experiencing serious adverse events (vs 7% with placebo). In a pooled analysis of the monotherapy trials, the most common adverse events (occurring in ≥ 5% of patients and at twice the incidence of placebo) reported during acute phase asenapine monotherapy for bipolar mania were somnolence, dizziness, extrapyramidal symptoms (EPS, other than akathisia) and increased bodyweight, which were similar in nature to those occurring during longer-term monotherapy with asenapine. EPS did not worsen in severity during longer-term asenapine monotherapy. Asenapine had minimal effects on plasma glucose, lipid and prolactin levels over both short- and longer-term treatment periods, and had little pro-arrhythmogenic potential. Further active comparator trials and longer-term tolerability and safety data are required. In the meantime, asenapine is a further option for the management of manic and/or mixed symptoms in patients with bipolar I disorder and may be of particular value for patients who are at high risk for metabolic abnormalities.

Review of the safety, efficacy, and side effect profile of asenapine in the treatment of bipolar 1 disorder

OBJECTIVE

Asenapine is approved for acute manic and mixed states in bipolar disorder. The objective is to review the efficacy of asenapine in bipolar disorder, with a particular focus on acceptability and adherence to treatment.

METHODS

FIVE CLINICAL TRIALS WERE CONDUCTED IN BIPOLAR DISORDER MANIC OR MIXED STATES: two 3-week trials (n = 976) comparing asenapine to placebo, a 9-week extension (n = 504), and a 40-week extension (n = 107). One trial was conducted comparing asenapine to placebo (n = 326) as adjunctive therapy for subjects with an incomplete response to lithium or valproate. All trials were conducted in the USA and internationally.

RESULTS

Asenapine was found to be efficacious for manic and mixed states in bipolar disorder compared with placebo control, and compares equally well to olanzapine on efficacy measures after 3 weeks of treatment. Asenapine was not found to be efficacious for depression symptoms. Common asenapine side effects in the 40-week extension trial were sedation, insomnia, and dizziness, and 31% reported clinically significant weight gain, compared with 55% reporting clinically significant weight gain with olanzapine. Additionally, 18% had clinically significant changes in fasting blood glucose levels compared to 22% of those on olanzapine. In terms of patient acceptability, one concern may be sublingual administration requiring no liquids or food for 10 minutes after dosing and a twice-daily regimen. Suggestions about addressing barriers to adherence and acceptability are provided.

CONCLUSION

Asenapine is a promising new medication in bipolar disorder. Asenapine in the long-term has a more favorable weight gain profile compared to olanzapine. No benefit was seen for depression symptoms, a major patient-reported concern. Some side effects do not remit after the short-term trials in at least 10% of patients.

Pharmacology and efficacy of asenapine for manic and mixed states in adults with bipolar disorder

Asenapine sublingual is a novel atypical antipsychotic approved in August 2009 for the acute treatment of schizophrenia, as well as for manic or mixed episodes as part of adult bipolar I disorder. Asenapine's in vitro profile is similar to other atypical antipsychotic agents insofar as there is higher affinity for serotonin 5-HT(2A) versus dopamine D(2) receptors. Asenapine exhibits a unique effect on monoamine, histamine and muscarinic receptor affinities, as well as effects on NMDA and AMPA receptors. This pharmacodynamic signature may mediate its symptom relief in positive, negative and mood symptoms, as well as conferring upon this agent an improved tolerability and safety profile when compared with some atypical agents. Asenapine has a relatively low propensity for changes in metabolic parameters, body composition, sedation/somnolence and extrapyramidal side effects, and is not associated with prolactin elevation or clinically significant electrocardiographic changes. Asenapine is available only in sublingual formulation, which has advantages (e.g., patient acceptance, compliance, difficulty swallowing) as well as disadvantages (i.e., patients are encouraged not to eat or drink within 10 min of administration). Its efficacy in mania is unequivocally established as is the sustaining of its acute antimanic effect. Its antidepressant and recurrence prevention effects in bipolar disorder are under investigation, as is its possible role in major depressive disorder.

Repeated effects of asenapine on adrenergic and cholinergic muscarinic receptors

Adrenergic (alpha1 and alpha2) and cholinergic muscarinic (M1-M5) receptor binding in rat forebrain was quantified after 4 wk of twice-daily subcutaneous administration of asenapine or vehicle. Asenapine (0.03, 0.1, and 0.3 mg/kg) produced increases in [3H]prazosin binding to alpha1-adrenergic receptors in the medial prefrontal cortex (mPFC: 30%, 39%, 57%) and dorsolateral frontal cortex (DFC: 27%, 37%, 53%) and increased [3H]RX821002 binding to alpha2-adrenergic receptors in mPFC (36%, 43%, 50%) and DFC (41%, 44%, 52%). Despite showing no appreciable affinity for muscarinic receptors, asenapine produced regionally selective increases in binding of [3H]QNB to M1-M5 receptors in mPFC (26%, 31%, 43%), DFC (27%, 34%, 41%), and hippocampal CA1 (40%, 44%, 42%) and CA3 (25%, 52%, 48%) regions. These regionally selective effects of asenapine on adrenergic and cholinergic muscarinic receptor subtypes may contribute to its beneficial clinical effects in the treatment of schizophrenia and bipolar disorder.

Asenapine

Asenapine is a novel psychopharmacological agent that binds with high affinity and specificity to numerous dopamine, serotonin, noradrenaline (norepinephrine) and histamine receptor subtypes. It is being developed for the treatment of schizophrenia and bipolar mania. In two randomized, controlled trials of asenapine monotherapy and in one randomized, controlled trial of adjunctive asenapine therapy in adult patients with bipolar I disorder, sublingual asenapine produced significantly greater reductions from baseline than placebo in clinician-assessed Young Mania Rating Scale (YMRS) total score at 3 weeks. In two randomized, controlled trials in adult patients with acute schizophrenia, treatment with asenapine reduced from baseline the clinician-assessed Positive and Negative Syndrome Scale (PANSS) total score to a significantly greater extent than placebo at 6 weeks. In schizophrenic patients with predominant, persistent, negative symptoms, asenapine at 26 weeks reduced the Negative Symptom Assessment (NSA-16) total score from baseline to an extent similar to that observed with olanzapine. Sublingual asenapine was generally well tolerated in clinical trials, with most treatment-emergent adverse events being of mild to moderate severity. Incidence rates of clinically significant weight gain, extrapyramidal symptoms, hyperprolactinaemia and alterations in glucose or lipid metabolism were generally low.

Asenapine monotherapy in the acute treatment of both schizophrenia and bipolar I disorder

Asenapine is a new atypical antipsychotic agent currently under development for the treatment of schizophrenia and bipolar disorder. It has high affinity for various receptors including antagonism at 5HT(2A), 5HT(2B), 5HT(2C), 5HT(6) and 5HT(7) serotonergic receptor subtypes, alpha(1A), alpha(2A), alpha(2B) and alpha(2C) adrenergic and D(3) and D(4) dopaminergic receptors. As with other atypicals, asenapine exhibits a high 5HT(2A):D(2) affinity ratio. Although similar to clozapine in its multi-target profile, it shows no appreciable affinity for muscarinic receptors. Asenapine has shown efficacy in alleviating both positive and negative symptoms of schizophrenia compared with placebo. Although promising, further studies are required in order to determine whether it has advantages over placebo and other antipsychotics in alleviating cognitive impairment associated with schizophrenia. It has also shown long-term efficacy comparable with olanzapine in bipolar I disorder. Asenapine is generally well tolerated and appears to be metabolically neutral. It has low propensity to cause weight gain and prolactin elevation. There were no concerns in the studies about its effects on the cardiovascular system and QTc prolongation. The incidence of extrapyramidal symptoms with asenapine however has been found to be higher than that with olanzapine. It may be a useful alternative to aripiprazole in schizophrenia and bipolar disorder in patients who are at high risk of metabolic abnormalities.