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

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.

Pharmacologic Treatment and Management of Bipolar Disorder in Adolescents

INTRODUCTION

The importance of the appropriate therapeutic interventions in children and adolescents with bipolar disorder (BD) cannot be overstated since treatment choices and their consequences may have effects into adulthood.

AREAS COVERED

Randomized clinical trials (RCTs) investigating treatment of mania, bipolar depression, and maintenance in adolescents with BD are reviewed. When RCTs are not available or are inadequate, naturalistic data or open studies are also reviewed.

EXPERT OPINION

Efficacy and safety of pharmaceutical agents in adolescents with BD appear to mirror adults with BD. Lithium/mood stabilizers are preferred first line agents over antipsychotic medications, but the latter are second line agents particularly in bipolar depression. When lithium is used, serum levels approaching 1.0 mEq/L are reasonable since younger people appear to require/tolerate higher levels. Among the antipsychotics, quetiapine appeared to be minimally better than risperidone while risperidone was associated with greater adverse events. Antipsychotics with antidepressant activity in adults, also appear to have antidepressant effects in youths. Use of antidepressants in bipolar depression is generally not recommended although it may be reasonable in specific clinical situations. The similarities between adolescent and adult outcomes suggest that it is reasonable to utilize adult data to aid with clinical decision making in adolescents with BD, especially when pediatric-specific data are unavailable.

Does the efficacy of asenapine in bipolar disorder increase in the presence of comorbidity with a substance use disorder? A naturalistic study

BACKGROUND

Asenapine is a second-generation antipsychotic approved in Europe for treating moderate-to-severe manic episodes in adults affected by type I bipolar disorder (BD-I). We aimed to compare its efficacy in psychiatric inpatients with BD-I, with or without substance use disorder (SUD).

METHODS

We administered flexible asenapine doses ranging from 5-20 mg/day to 119 voluntarily hospitalized patients with Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision (DSM-IV-TR) BD-I diagnosis, with or without SUD. Patients were assessed with clinician-rated questionnaires [i.e. Brief Psychiatric Rating Scale (BPRS), Young Mania Rating Scale (YMRS), Hamilton Depression Rating Scale (HDRS), Hamilton Anxiety Rating Scale (HARS), and Global Assessment of Functioning (GAF)]. Assessments were carried out at baseline (T0, prior to treatment), and 3 (T1), 7 (T2), 15 (T3), and 30 days (T4) after starting treatment for all clinical scales and at T0 and T4 for the GAF.

RESULTS

Patients improved on all scales (p < 0.001) across all timepoints, as shown both by paired-sample comparisons and by applying a repeated-measures, generalized linear model (GLM). Patients without comorbid SUD showed greater reductions in BPRS scores at T2 and T3, greater reduction in YMRS scores at T3, and lower HARS scores at all timepoints. HDRS scores did not differ between the two groups at any timepoint. However, the reduction in HARS scores in the comorbid group was stronger than in the BD-I only group, albeit not significantly. Side effects were few and mild-to-moderate.

CONCLUSIONS

The open-label design and the relatively short observation period may expose to both type I and type II statistical errors (false positive and false negatives). Asenapine showed effectiveness and safety in hospitalized BD-I patients. Its effect was stronger in patients without comorbid SUD.

Asenapine for the Acute Treatment of Pediatric Manic or Mixed Episode of Bipolar I Disorder

OBJECTIVE

To evaluate asenapine versus placebo in 403 patients aged 10 to 17 years with bipolar I disorder currently in manic or mixed episodes.

METHOD

In this double-blind, placebo-controlled, international trial, patients were randomized 1:1:1:1 to placebo, asenapine 2.5, 5, or 10 mg b.i.d. (twice daily). Primary efficacy measure was change from baseline in Young-Mania Rating Scale (YMRS) total score at day 21. Analyses of patients with/without attention-deficit/hyperactivity disorder (ADHD) and with/without stimulant use were performed.

RESULTS

The mean difference in asenapine versus placebo in YMRS was -3.2 (p = .0008), -5.3 (p < .001), and -6.2 (p < .001) for asenapine 2.5, 5, and 10 mg b.i.d., respectively. Treatment-emergent adverse events with an incidence ≥5% and at least twice placebo were somnolence, sedation, hypoesthesia oral, paresthesia oral, and increased appetite. The asenapine groups had a higher incidence of ≥7% weight gain (range, 8.0%-12.0%) versus placebo (1.1%; p < .05). The mean change from baseline in fasting insulin was larger for patients treated with asenapine than those with placebo (asenapine 2.5 mg b.i.d.: 73.375 pmol/L; asenapine 5 mg b.i.d.: 114.042 pmol/L; asenapine 10 mg b.i.d.: 59.846 pmol/L; placebo: 3.690 pmol/L). The mean changes from baseline for lipid parameters and glucose were also larger in asenapine groups than in the placebo group. No safety differences were observed with respect to ADHD and stimulant use.

CONCLUSION

All asenapine doses versus placebo were superior based on change in YMRS at day 21. Asenapine was generally well tolerated in patients aged 10 to 17 years with bipolar I disorder in manic or mixed states. Increases in weight and fasting insulin were associated with asenapine. Clinical trial registration information-Efficacy and Safety of Asenapine Treatment for Pediatric Bipolar Disorder; http://clinicaltrials.gov; NCT01244815.

The effects of novel and newly approved antipsychotics on serum prolactin levels: a comprehensive review

Since the 1970s, clinicians have increasingly become more familiar with hyperprolactinemia (HPRL) as a common adverse effect of antipsychotic medication, which remains the cornerstone of pharmacological treatment for patients with schizophrenia. Although treatment with second-generation antipsychotics (SGAs) as a group is, compared with use of the first-generation antipsychotics, associated with lower prolactin (PRL) plasma levels, the detailed effects on plasma PRL levels for each of these compounds in reports often remain incomplete or inaccurate. Moreover, at this moment, no review has been published about the effect of the newly approved antipsychotics asenapine, iloperidone and lurasidone on PRL levels. The objective of this review is to describe PRL physiology; PRL measurement; diagnosis, causes, consequences and mechanisms of HPRL; incidence figures of (new-onset) HPRL with SGAs and newly approved antipsychotics in adolescent and adult patients; and revisit lingering questions regarding this hormone. A literature search, using the MEDLINE database (1966-December 2013), was conducted to identify relevant publications to report on the state of the art of HPRL and to summarize the available evidence with respect to the propensity of the SGAs and the newly approved antipsychotics to elevate PRL levels. Our review shows that although HPRL usually is defined as a sustained level of PRL above the laboratory upper limit of normal, limit values show some degree of variability in clinical reports, making the interpretation and comparison of data across studies difficult. Moreover, many reports do not provide much or any data detailing the measurement of PRL. Although the highest rates of HPRL are consistently reported in association with amisulpride, risperidone and paliperidone, while aripiprazole and quetiapine have the most favorable profile with respect to this outcome, all SGAs can induce PRL elevations, especially at the beginning of treatment, and have the potential to cause new-onset HPRL. Considering the PRL-elevating propensity of the newly approved antipsychotics, evidence seems to indicate these agents have a PRL profile comparable to that of clozapine (asenapine and iloperidone), ziprasidone and olanzapine (lurasidone). PRL elevations with antipsychotic medication generally are dose dependant. However, antipsychotics having a high potential for PRL elevation (amisulpride, risperidone and paliperidone) can have a profound impact on PRL levels even at relatively low doses, while PRL levels with antipsychotics having a minimal effect on PRL, in most cases, can remain unchanged (quetiapine) or reduce (aripiprazole) over all dosages. Although tolerance and decreases in PRL values after long-term administration of PRL-elevating antipsychotics can occur, the elevations, in most cases, remain above the upper limit of normal. PRL profiles of antipsychotics in children and adolescents seem to be the same as in adults. The hyperprolactinemic effects of antipsychotic medication are mostly correlated with their affinity for dopamine D2 receptors at the level of the anterior pituitary lactotrophs (and probably other neurotransmitter mechanisms) and their blood-brain barrier penetrating capability. Even though antipsychotics are the most common cause of pharmacologically induced HPRL, recent research has shown that HPRL can be pre-existing in a substantial portion of antipsychotic-naïve patients with first-episode psychosis or at-risk mental state.

Fluoxetine impairs GABAergic signaling in hippocampal slices from neonatal rats

Fluoxetine (Prozac), an antidepressant known to selectively inhibit serotonin reuptake, is widely used to treat mood disorders in women suffering from depression during pregnancy and postpartum period. Several lines of evidence suggest that this drug, which crosses the human placenta and is secreted into milk during lactation, exerts its action not only by interfering with serotoninergic but also with GABAergic transmission. GABA is known to play a crucial role in the construction of neuronal circuits early in postnatal development. The immature hippocampus is characterized by an early type of network activity, the so-called Giant Depolarizing Potentials (GDPs), generated by the synergistic action of glutamate and GABA, both depolarizing and excitatory. Here we tested the hypothesis that fluoxetine may interfere with GABAergic signaling during the first postnatal week, thus producing harmful effects on brain development. At micromolar concentrations fluoxetine severely depressed GDPs frequency (IC50 22 μM) in a reversible manner and independently of its action on serotonin reuptake. This effect was dependent on a reduced GABAergic (but not glutamatergic) drive to principal cells most probably from parvalbumin-positive fast spiking neurons. Cholecystokinin-positive GABAergic interneurons were not involved since the effects of the drug persisted when cannabinoid receptors were occluded with WIN55,212-2, a CB1/CB2 receptor agonist. Fluoxetine effects on GABAergic transmission were associated with a reduced firing rate of both principal cells and interneurons further suggesting that changes in network excitability account for GDPs disruption. This may have critical consequences on the functional organization and stabilization of neuronal circuits early in postnatal development.

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.

Mood stabilizers for patients with bipolar disorder: the state of the art

Bipolar disorder (BD) is a prevalent and disabling condition, often comorbid with other medical and psychiatric conditions and frequently misdiagnosed. International treatment guidelines for BD recommend the use of mood stabilizers - either in monotherapy or in association - as the gold standard in both acute and long-term therapy. Commonly used in the clinical practice of BD, mood stabilizers have represented an evolving field over the last few years. The concept of stabilization, in fact, has been stressed as the ultimate objective of the treatment of BD, given the chronic and recurrent nature of the illness, which accounts for its significant levels of impairment and disability. To date, different compounds are included within the broad class of mood stabilizers, with lithium, anticonvulsants and, more recently, atypical antipsychotics being the most representative agents. This article is aimed at providing an updated review of the available literature in relation to the role of mood stabilizers in BD, with particular emphasis on their mechanism of action, main clinical aspects and specific use in the different phases of BD treatment, according to the most recently published international treatment guidelines.

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.

Asenapine: a review of acute and extension phase data in bipolar disorder

The second generation atypical antipsychotic, asenapine (Saphris), was approved by the US FDA (August 2009) for the acute treatment of manic or mixed episodes with or without psychotic features associated with bipolar I disorder in adults as well as the acute treatment of schizophrenia. Asenapine exhibits a high affinity for and antagonism at several serotonergic (5-HT(2A-C), 5HT(5A), 5HT(6), 5HT(7)), dopaminergic (D(2), D(3)), alpha-adrenergic (α(1) and α(2)), and histaminergic (H1, H2) receptor subtypes. Asenapine is the first atypical antipsychotic formulated as a fast-dissolving, rapidly absorbed sublingual tablet. Asenapine was evaluated in adults with bipolar I disorder, manic or mixed episodes with or without psychotic features. Two identically designed 3-week registration trials confirmed the efficacy of asenapine relative to placebo in studies that included olanzapine as an active control. The placebo-subtracted rate of EPS (excluding akathisia) is 5% whereas the placebo-subtracted rate of akathisia was 2%. The placebo-subtracted rate of clinically significant weight gain (≥7%) with asenapine was approximately 5% during the 3-week acute mania trials. A 9- extension trial indicated that 19% of asenapine patients will experience clinically significant weight gain. Clinically significant metabolic abnormalities were not observed during the acute and/or extension trials. Asenapine can be associated with somnolence (asenapine 24%, placebo 6%) and does not appear to be associated with clinically significant changes in vital signs, laboratory parameters, or electrocardiographic changes. Bipolar depression and recurrence prevention studies are required to fully characterize this novel agent's position in the treatment of bipolar disorder.