Characterization of aripiprazole partial agonist activity at human dopamine D3 receptors

Evaluating the efficacy and safety of the currently available once-every-two months long-acting injectable formulations of aripiprazole for the treatment of schizophrenia or as a maintenance monotherapy for bipolar I disorder in adults

INTRODUCTION

An aripiprazole long-acting injectable (LAI) antipsychotic is now available for gluteal administration every 2 months via two different formulations: aripiprazole lauroxil (AL) and aripiprazole monohydrate (Ari 2MRTU). These longer dosing regimens of aripiprazole LAI offer new potential benefits for patients.

AREAS COVERED

The authors review the evidence supporting the efficacy and safety of aripiprazole LAIs given every 2 months for the treatment of schizophrenia or bipolar disorder (BD) in adults. The article culminates with the authors' expert perspectives on the subject.

EXPERT OPINION

AL 1064 mg every 2 months has established efficacy for the treatment of schizophrenia based on pharmacokinetic bridging studies and prospective data for treatment of an acute exacerbation of schizophrenia. In an open-label trial, Ari 2MRTU showed efficacy for the treatment of schizophrenia and BD type I based on pharmacokinetic parameters (comparable to aripiprazole once-monthly 400 mg); it also showed efficacy regarding the secondary endpoints. Multiple doses of AL 1064 mg or Ari 2MRTU 960 mg are generally well tolerated, in line with the safety profile of oral aripiprazole, with the exception of the injection-site reactions. While AL may require a 1-day initiation regimen, Ari 2MRTU 960 covers all the recommended doses of oral aripiprazole (10-20 mg).

Dorsal BNST DRD2+ neurons mediate sex-specific anxiety-like behavior induced by chronic social isolation

The dorsal bed nucleus of stria terminalis (dBNST) is a pivotal hub for stress response modulation. Dysfunction of dopamine (DA) network is associated with chronic stress, but the roles of DA network of dBNST in chronic stress-induced emotional disorders remain unclear. We examine the role of dBNST Drd1⁺ and Drd2⁺ neurons in post-weaning social isolation (PWSI)-induced behavior deficits. We find that male, but not female, PWSI rats exhibit negative emotional phenotypes and the increase of excitability and E-I balance of dBNST Drd2⁺ neurons. More importantly, hypofunction of dBNST Drd2 receptor underlies PWSI-stress-induced male-specific neuronal plasticity change of dBNST Drd2⁺ neurons. Furthermore, chemogenetic activation of dBNST Drd2⁺ neurons is sufficient to induce anxiogenic effects, while Kir4.1-mediated chronic inhibition of dBNST Drd2⁺ neurons ameliorate PWSI-induced anxiety-like behaviors. Our findings reveal an important neural mechanism underlying PWSI-induced sex-specific behavioral abnormalities and potentially provide a target for the treatment of social stress-related emotional disorder.

Aripiprazole IM depot as an option for the treatment of bipolar disorder

Introduction: Long-acting injectable (LAI) antipsychotic drugs are developed to reduce daily intake need and to overcome treatment non-adherence. Aripiprazole IM depot refers to two long-acting aripiprazole formulations, once monthly monohydrate (AOM) and aripiprazole lauroxil. AOM has been approved for schizophrenia since 2012 and for bipolar disorder since 2017. Aripiprazole lauroxil is approved for schizophrenia, not for bipolar disorder.Areas covered: To assess the effect of AOM in bipolar disorder, the authors searched PubMed and ClinicalTrials.gov for randomized trials using AOM in patients with bipolar disorder. Included were four studies covering efficacy, functioning, quality of life, and safety/tolerability. Studies lasted 12 months.Expert opinion: AOM reduced symptoms of patients with bipolar disorder and a manic episode, increased functioning and quality of life, and protected from recurrence of manic episodes. It proved to be safe/tolerable, with only akathisia occurring in ≥10% of cases and more frequently than with placebo. However, there were only 143 patients receiving AOM in the considered studies. Included studies were backed in their conclusions by other literature, but they come from 2017-2018. No studies are expected or planned in the near future. Aripiprazole lauroxil has not applied for approval in bipolar disorder and there is no sign it will.

A Split Luciferase Complementation Assay for the Quantification of β-Arrestin2 Recruitment to Dopamine D2-Like Receptors

Investigations on functional selectivity of GPCR ligands have become increasingly important to identify compounds with a potentially more beneficial side effect profile. In order to discriminate between individual signaling pathways, the determination of β-arrestin2 recruitment, in addition to G-protein activation, is of great value. In this study, we established a sensitive split luciferase-based assay with the ability to quantify β-arrestin2 recruitment to D_2long and D₃ receptors and measure time-resolved β-arrestin2 recruitment to the D_2long receptor after agonist stimulation. We were able to characterize several standard (inverse) agonists as well as antagonists at the D_2longR and D₃R subtypes, whereas for the D_4.4R, no β-arrestin2 recruitment was detected, confirming previous reports. Extensive radioligand binding studies and comparisons with the respective wild-type receptors confirm that the attachment of the Emerald luciferase fragment to the receptors does not affect the integrity of the receptor proteins. Studies on the involvement of GRK2/3 and PKC on the β-arrestin recruitment to the D_2longR and D₃R, as well as at the D₁R using different kinase inhibitors, showed that the assay could also contribute to the elucidation of signaling mechanisms. Its broad applicability, which provides concentration-dependent and kinetic information on receptor/β-arrestin2 interactions, renders this homogeneous assay a valuable method for the identification of biased agonists.

Altered dopamine D3 receptor gene expression in MAM model of schizophrenia is reversed by peripubertal cannabidiol treatment

Gestational methylazoxymethanol acetate (MAM) treatment produces offspring with adult phenotype relevant to schizophrenia, including positive- and negative-like symptoms, cognitive deficits, dopaminergic dysfunction, structural and functional abnormalities. Here we show that adult rats prenatally treated with MAM at gestational day 17 display significant increase in dopamine D3 receptor (D3) mRNA expression in prefrontal cortex (PFC), hippocampus and nucleus accumbens, accompanied by increased expression of dopamine D2 receptor (D2) mRNA exclusively in the PFC. Furthermore, a significant change in the blood perfusion at the level of the circle of Willis and hippocampus, paralleled by the enlargement of lateral ventricles, was also detected by magnetic resonance imaging (MRI) techniques. Peripubertal treatment with the non-euphoric phytocannabinoid cannabidiol (30 mg/kg) from postnatal day (PND) 19 to PND 39 was able to reverse in MAM exposed rats: i) the up-regulation of the dopamine D3 receptor mRNA (only partially prevented by haloperidol 0.6 mg/kg/day); and ii) the regional blood flow changes in MAM exposed rats. Molecular modelling predicted that cannabidiol could bind preferentially to dopamine D3 receptor, where it may act as a partial agonist according to conformation of ionic-lock, which is highly conserved in GPCRs. In summary, our results demonstrate that the mRNA expression of both dopamine D2 and D3 receptors is altered in the MAM model; however only the transcript levels of D3 are affected by cannabidiol treatment, likely suggesting that this gene might not only contribute to the schizophrenia symptoms but also represent an unexplored target for the antipsychotic activity of cannabidiol.

Comorbidity between ADHD and anxiety disorders across the lifespan

Objectives: Attention deficit/hyperactivity disorder (ADHD) and anxiety disorders are among the most common psychiatric disorders with a 25% comorbidity rate with each other. In this study, we overview the comorbidity between ADHD and anxiety disorders in a longitudinal perspective across the lifespan and we discuss possible therapeutic strategies.Methods: A literature search was performed using PubMed to identify clinical studies assessing comorbidity between ADHD and anxiety disorders from childhood to adulthood.Results: Anxiety disorders may substantially change the presentation, the prognosis, and the treatment of ADHD itself. In childhood, the presence of generalised anxiety disorder, could prevent the typical inhibitory dysfunction present in ADHD, in adolescence may increase the deficit of working memory, and in adulthood may enhance the presence of sleep problems. Individuals with comorbid ADHD and anxiety disorders would benefit from adjunctive psychosocial or adjunctive pharmacotherapy interventions to cognitive behavioural treatment.Conclusions: The management of individuals with comorbid ADHD and anxiety disorders could be challenging for clinicians, and assessing the developmental course is crucial in order to shed light on individualised treatment.KeypointsThe comorbidity between ADHD and anxiety disorders changes the clinical presentation, the prognosis and treatment of patients with ADHD across lifespan.ADHD and anxiety disorders shared common neurobiological dysfunctions but have also different neurobiological abnormalities suggesting that they are different diagnoses.These patients are less likely to benefit from cognitive behavioural treatment strategies alone and often need adjunctive pharmacological treatments.Studies that evaluated the response to MPH reported conflicting results. These patients could respond less well and get more unpleasant arousal side-effects, but these findings need to be confirmed.For his unique mechanism of action, low dose aripiprazole treatment in adolescents and adults with this comorbid condition could be an intriguing avenue of exploration.

Further Evidence Regarding the Important Role of Chlorine Atoms of Aripiprazole on Binding to the Site II Area of Human Albumin

Previously, we reported on the high-affinity binding of aripiprazole (ARP), an antipsychotic drug, to human albumin and the role of the chlorine atom of ARP on this binding. In this study, we investigated the binding mode of ARP to human albumin in detail using ARP derivatives and several animal-derived albumins. ARP bound strongly to human and dog albumin. The circular dichroism (CD) spectra of ARP bound to human and dog albumin were also similar. Deschloro-ARP bound less strongly to all of the albumin species compared to ARP, and the shapes of CD spectra were similar for all albumin species. CD spectra of dimethyl-ARP, for which chlorine atoms were substituted methyl groups, were quite similar to that of deschloro-ARP. In displacement experiments, competitive binding was observed between ARP and deschloro-ARP. These results suggest that the chlorine atoms in ARP are involved in the binding modes of ARP for human and dog albumins, whereas ARP and deschloro-ARP appear to share the same binding region in site II. The aforementioned results imply that compounds having a chlorine atom bind more strongly to plasma proteins, resulting in a long blood retention time. Therefore, findings reported here may provide the basically useful data for drug design.

Pharmacotherapy for amphetamine dependence: A systematic review

BACKGROUND

Demand for treatment for amphetamine use is increasing internationally. Establishing effective pharmacotherapy provides broader treatment options for people who are dependent on amphetamine and may encourage engagement in evidence-based behavioral treatment. This study aimed to identify medicines that have potential in improving treatment outcomes for people who are dependent on amphetamines.

METHODS

Medline, PsycINFO, Embase and the Cochrane Database of Systematic Reviews were searched from 1997 to 2012 and again from 2013 to 2016. Studies on medications for amphetamine/methamphetamine dependence treatment were selected and assessed by two independent researchers. A meta-narrative review approach was used to synthesize results.

RESULTS

A total of 49 studies investigating 20 potential pharmacotherapies were eligible for inclusion. Of these, 35 studies related to 33 level II quality randomized controlled trials (RCTs). Five medications were subject to multiple RCTs. Four of these medicines demonstrated some limited evidence of benefit for reducing amphetamine use: methylphenidate (as reported in three studies), bupropion (in three studies), modafinil (two studies), and naltrexone (one study). Four RCTs of dexamphetamine suggest its benefit on secondary outcomes such as treatment retention, but not for reducing amphetamine use. Six other medicines indicate the potential for efficacy, but the number of studies is too small to draw conclusions.

CONCLUSIONS

No medicine has as yet demonstrated sufficient, consistent evidence of effectiveness to support its use in routine treatment. High study drop-out and poor medication adherence limits the strength of evidence and raises important clinical questions about how to improve treatment engagement and outcomes.

Head-to-head comparison of 1-year aripiprazole long-acting injectable (LAI) versus paliperidone LAI in comorbid psychosis and substance use disorder: impact on clinical status, substance craving, and quality of life

BACKGROUND

To overcome nonadherence in patients with psychosis switch to long-acting injectable (LAI) antipsychotic formulations is adopted. Most oral versus LAI comparisons showed similar antipsychotic responses. Psychoses often overlap with substance use disorder (SUD). Head-to-head LAI comparisons have hitherto focused only on non-comorbid populations.

OBJECTIVE

The objective of this study was to compare two LAIs, administered for 12 months, in initially hospitalized patients with psychosis comorbid with SUD in their clinical and quality of life (QoL) outcomes.

PATIENTS AND METHODS

Inpatients were recruited during 2016 and switched randomly to 400 mg intramuscular aripiprazole monohydrate (AM) (N=50) or to 100 mg intramuscular paliperidone palmitate (PP) once-monthly (N=51); patients were discharged and followed up for 12 months. Patients were rated at baseline and after 1 year through the Clinical Global Impression scale - severity (CGIs), substance craving intensity was rated through a visual analog scale for substance craving, and QoL through the World Health Organization (WHOQOL-BREF) scale. We addressed confounders with backward stepwise logistic regression and three-way analysis of variance.

RESULTS

PP were older and had more cases of schizophrenia spectrum and less bipolar disorders than AM, but AM had a stronger craving for substances at baseline. Both LAIs were associated with significant improvements in all outcomes, with AM displaying stronger effect sizes than PP. The two groups did not differ on baseline WHOQOL-BREF scores in any domain, but at the 1-year follow-up, AM fared better on all domains. The two groups did not differ in final severity, but PP scored higher than AM in craving at the 1-year endpoint.Limitation: The CGIs is not a refined tool for severity and the substance craving may be subject to recall bias.

CONCLUSION

1-year AM and PP was followed by improved clinical status and QoL and reduced substance craving in a population with psychosis and SUD comorbidity. AM, compared to PP, improved craving and QoL at the 1-year follow-up.

Late Reduction of Cocaine Cravings in a Randomized, Double-Blind Trial of Aripiprazole vs Perphenazine in Schizophrenia and Comorbid Cocaine Dependence

PURPOSE

Co-occurring schizophrenia spectrum disorder and International Statistical Classification of Diseases, 10th Revision cocaine dependence present a particularly destructive constellation that is often difficult to treat. Both conditions raise dopamine transmission effects in the brain. Traditional neuroleptics block dopamine receptors, whereas aripiprazole modulates dopamine activity as an agonist/antagonist. We tested whether dopamine modulation is superior to dopamine blocking in dual-diagnosis patients.

METHODS

In a randomized, double-blind, comparison design, cocaine-dependent schizophrenic subjects actively using cocaine received either aripiprazole or perphenazine in an 8-week trial. Primary outcome targeted cocaine-free urine sample proportions, whereas cocaine craving scores were a secondary variable.

RESULTS

Subjects (N = 44) randomized (n = 22 per group) did not differ at baseline. The proportion of cocaine-free urine samples did not differ by medication group. Contrasting weeks 3 to 5 vs 6 to 8 revealed significant late reductions in craving with aripiprazole. On the respective 5-point subscales, craving intensity decreased by 1.53 ± 0.43 (P < 0.0005) points, craving frequency by 1.4 ± 0.40 (P > 0.0004) points, and craving duration by 1.76 ± 0.44 (P > 0.0001) points.

CONCLUSIONS

A drug effect of aripiprazole on craving items appeared at week 6 of treatment, on average, and was not seen before that length of drug exposure. The data suggest that dopamine modulation reduces cocaine cravings but requires an acclimation period. To understand the mechanism of action better, a trial of depot aripiprazole may be useful. Clinically, a reduction in craving potentially offers a clearer focus for ongoing behavioral treatment. It may also offer a longer-term treatment effect with respect to the severity of relapse.

Aripiprazole prevents renal ischemia/reperfusion injury in rats, probably through nitric oxide involvement

Renal ischemia/reperfusion (I/R) injury is strongly related to morbidity and mortality. Oxidative stress, inflammation, and apoptosis play key roles in renal dysfunction following renal I/R. Aripiprazole is an atypical antipsychotic which used for the treatment of schizophrenia and bipolar disorder. Recent studies have reported aripiprazole as displaying certain anti-inflammatory effects. Regarding the underlying mechanisms of renal ischemia-reperfusion, therefore, nephroprotective effects might be predicted to be seen with aripiprazole. I/R injury was induced by bilateral clamping of the renal pedicles (45min) followed by reperfusion (24h). The mechanism of aripiprazole-mediated nephroprotection was explored by a combined use of aripiprazole and L-NAME (non-selective nitric oxide synthase inhibitor). Animals were given aripiprazole (2.5, 5, 10 and 20mg/kg) intraperitoneally, 30min before ischemia. L-NAME was administered before the aripiprazole injection. Serum creatinine and blood urea nitrogen were assessed after 24h of reperfusion. Serum levels of malondialdehyde (MDA), TNF-α and IL-1β were measured for rats treated with aripiprazole. The extent of necrosis was measured by the stereology method. Ischemia/reperfusion caused significant renal dysfunction and marked renal injury. Aripiprazole reduced creatinine and blood urea nitrogen. Serum levels of MDA, IL-1β and TNF-α were significantly lower in the aripiprazole group. Aripiprazole treatment also decreased the volume of kidney necrosis. The administration of L-NAME reversed the renoprotective effect of aripiprazole on BUN and creatinine, but enhanced the anti-necrotic effect of aripiprazole. The results show that a single dose of aripiprazole significantly improved renal function following ischemia/reperfusion injury - probably through the involvement of nitric oxide.

Classics in Chemical Neuroscience: Aripiprazole

Aripiprazole was the first antipsychotic developed to possess agonist properties at dopamine D₂ autoreceptors, a groundbreaking strategy that presented a new vista for schizophrenia drug discovery. The dopamine D₂ receptor is the crucial target of all extant antipsychotics, and all developed prior to aripiprazole were D₂ receptor antagonists. Extensive blockade of these receptors, however, typically produces extrapyramidal (movement) side effects, which plagued first-generation antipsychotics, such as haloperidol. Second-generation antipsychotics, such as clozapine, with unique polypharmacology and D₂ receptor binding kinetics, have significantly lower risk of movement side effects but can cause myriad additional ones, such as severe weight gain and metabolic dysfunction. Aripiprazole's polypharmacology, characterized by its unique agonist activity at dopamine D₂ and D₃ and serotonin 5-HT_1A receptors, as well as antagonist activity at serotonin 5-HT_2A receptors, translates to successful reduction of positive, negative, and cognitive symptoms of schizophrenia, while also mitigating risk of weight gain and movement side effects. New observations, however, link aripiprazole to compulsive behaviors in a small group of patients, an unusual side effect for antipsychotics. In this review, we discuss the chemical synthesis, pharmacology, pharmacogenomics, drug metabolism, and adverse events of aripiprazole, and we present a current understanding of aripiprazole's neurotherapeutic mechanisms, as well as the history and importance of aripiprazole to neuroscience.

A three-parameter two-state model of receptor function that incorporates affinity, efficacy, and signal amplification

A generalized model of receptor function is proposed that relies on the essential assumptions of the minimal two-state receptor theory (i.e., ligand binding followed by receptor activation), but uses a different parametrization and allows nonlinear response (transduction) for possible signal amplification. For the most general case, three parameters are used: Kd, the classic equilibrium dissociation constant to characterize binding affinity; ε, an intrinsic efficacy to characterize the ability of the bound ligand to activate the receptor (ranging from 0 for an antagonist to 1 for a full agonist); and γ, a gain (amplification) parameter to characterize the nonlinearity of postactivation signal transduction (ranging from 1 for no amplification to infinity). The obtained equation, E/Emax=εγLεγ+1-εL+Kd, resembles that of the operational (Black and Leff) or minimal two-state (del Castillo-Katz) models, E/Emax=τLτ+1L+Kd, with εγ playing a role somewhat similar to that of the τ efficacy parameter of those models, but has several advantages. Its parameters are more intuitive as they are conceptually clearly related to the different steps of binding, activation, and signal transduction (amplification), and they are also better suited for optimization by nonlinear regression. It allows fitting of complex data where receptor binding and response are measured separately and the fractional occupancy and response are mismatched. Unlike the previous models, it is a true generalized model as simplified forms can be reproduced with special cases of its parameters. Such simplified forms can be used on their own to characterize partial agonism, competing partial and full agonists, or signal amplification.

Possible biomarkers modulating haloperidol efficacy and/or tolerability

Haloperidol (HP) is widely used in the treatment of several forms of psychosis. Despite of its efficacy, HP use is a cause of concern for the elevated risk of adverse drug reactions. adverse drug reactions risk and HP efficacy greatly vary across subjects, indicating the involvement of several factors in HP mechanism of action. The use of biomarkers that could monitor or even predict HP treatment impact would be of extreme importance. We reviewed the elements that could potentially be used as peripheral biomarkers of HP effectiveness. Although a validated biomarker still does not exist, we underlined the several potential findings (e.g., about cytokines, HP metabolites and genotypic biomarkers) which could pave the way for future research on HP biomarkers.

Add-on effects of a low-dose aripiprazole in resolving hyperprolactinemia induced by risperidone or paliperidone

This study investigated the effects of a low-dose aripiprazole adjunctive treatment for risperidone- or paliperidone-induced hyperprolactinemia in Han Chinese women with schizophrenia. After 4 weeks of risperidone or paliperidone treatment, 60 out of 66 patients improved significantly and experienced hyperprolactinemia. They were randomly assigned to the treatment group (aripiprazole adjunctive treatment) (n=30) or control group (non-adjunctive treatment) (n=30). The dosage of risperidone and paliperidone were maintained; and aripiprazole was maintained at 5mg/day during the 8-week study period. The prolactin levels at the end of the 8th week were significantly lower in the treatment group than in the control group. The estradiol level correlated negatively with serum prolactin level both in the treatment group and the control group at the end of the 8th week and the 4th week respectively. The Positive and Negative Syndrome Scale score improved significantly during the 8-week study period in both groups. The incidence of treatment-emergent adverse event was similar in two groups. Low-dose aripiprazole adjunctive treatment is effective in relieving risperidone- and paliperidone-induced hyperprolactinemia in female schizophrenic patients without increasing adverse event.

Unique Effects of Acute Aripiprazole Treatment on the Dopamine D2 Receptor Downstream cAMP-PKA and Akt-GSK3β Signalling Pathways in Rats

Aripiprazole is a wide-used antipsychotic drug with therapeutic effects on both positive and negative symptoms of schizophrenia, and reduced side-effects. Although aripiprazole was developed as a dopamine D₂ receptor (D₂R) partial agonist, all other D₂R partial agonists that aimed to mimic aripiprazole failed to exert therapeutic effects in clinic. The present in vivo study aimed to investigate the effects of aripiprazole on the D₂R downstream cAMP-PKA and Akt-GSK3β signalling pathways in comparison with a D₂R antagonist – haloperidol and a D₂R partial agonist – bifeprunox. Rats were injected once with aripiprazole (0.75mg/kg, i.p.), bifeprunox (0.8mg/kg, i.p.), haloperidol (0.1mg/kg, i.p.) or vehicle. Five brain regions – the prefrontal cortex (PFC), nucleus accumbens (NAc), caudate putamen (CPu), ventral tegmental area (VTA) and substantia nigra (SN) were collected. The protein levels of PKA, Akt and GSK3β were measured by Western Blotting; the cAMP levels were examined by ELISA tests. The results showed that aripiprazole presented similar acute effects on PKA expression to haloperidol, but not bifeprunox, in the CPU and VTA. Additionally, aripiprazole was able to increase the phosphorylation of GSK3β in the PFC, NAc, CPu and SN, respectively, which cannot be achieved by bifeprunox and haloperidol. These results suggested that acute treatment of aripiprazole had differential effects on the cAMP-PKA and Akt-GSK3β signalling pathways from haloperidol and bifeprunox in these brain areas. This study further indicated that, by comparison with bifeprunox, the unique pharmacological profile of aripiprazole may be attributed to the relatively lower intrinsic activity at D₂R.

The effect of acute aripiprazole treatment on chemically and electrically induced seizures in mice: The role of nitric oxide

Aripiprazole is an antipsychotic drug which acts through dopamine and serotonin receptors. Aripiprazole was noted to have antiseizure effects in a study on mice, while it induced seizures in a few human case reports. Dopaminergic and serotonergic systems relate to nitric oxide, and aripiprazole also has effects on dopamine and serotonin receptors. This study investigated the effects of aripiprazole on seizures and the potential role of nitric oxide in the process. The following three models were examined to explore the role of aripiprazole on seizures in mice: 1 - pentylenetetrazole administered intravenously, 2 - pentylenetetrazole administered intraperitoneally, and 3 - electroshock. Aripiprazole administration delayed clonic seizure in intravenous and intraperitoneal pentylenetetrazole models. In the electroshock-induced seizure model, tonic seizure and mortality protection percent were increased after aripiprazole administration. In intraperitoneal administration of pentylenetetrazole, aripiprazole effects on clonic seizure latency were significantly decreased when l-NAME - a nonselective nitric oxide synthase (NOS) inhibitor, 7-nitroindazole - a selective neuronal NOS (nNOS) inhibitor, or aminoguanidine - a selective inducible NOS (iNOS) inhibitor was injected before aripiprazole administration. In the intravenous pentylenetetrazole method, administration of l-NAME or aminoguanidine inhibited aripiprazole effects on clonic seizure threshold. Aminoguanidine or l-NAME administration decreased aripiprazole-induced protection against tonic seizures and death in the electroshock model. In both intravenous and intraperitoneal seizure models, aripiprazole and l-arginine coadministration delayed the onset of clonic seizures. Moreover, it increased protection against tonic seizures and death in intraperitoneal pentylenetetrazole and electroshock models. In conclusion, the release of nitric oxide via iNOS or nNOS may be involved in anticonvulsant properties of aripiprazole.

Patterns of response to aripiprazole, lithium, haloperidol, and placebo across factor scores of mania

Background

A previous factor analysis of Young Mania Rating Scale and Montgomery-Åsberg Depression Rating Scale items identified composite factors of depression, mania, sleep disturbance, judgment/impulsivity, and irritability/hostility as major components of psychiatric symptoms in acute mania or mixed episodes in a series of trials of antipsychotics. However, it is unknown whether these factors predict treatment outcome.

Methods

Data from six double-blind, randomized, controlled clinical trials with aripiprazole in acute manic or mixed episodes in adults with bipolar I disorder were pooled for this analysis and the previously identified factors were examined for their value in predicting treatment outcome. Treatment efficacy was assessed for aripiprazole (n = 1,001), haloperidol (n = 324), lithium (n = 155), and placebo (n = 694) at baseline, days 4, 7, and 10, and then weekly to study end. Mean change in factor scores from baseline to week 3 was assessed by receiver operating characteristics curves for percentage factor change at day 4 and week 1.

Results

Subjects receiving aripiprazole, haloperidol, and lithium significantly improved mania factor scores versus placebo. Factors most predictive of endpoint efficacy for aripiprazole were judgment/impulsivity at day 4 and mania at week 1. Optimal factor score improvement for outcome prediction was approximately 40% to 50%. Early efficacy predicted treatment outcome across all factors; however, response at week 1 was a better predictor than response at day 4.

Conclusions

This analysis confirms clinical benefits in early treatment/assessment for subjects with bipolar mania and suggests that certain symptom factors in mixed or manic episodes may be most predictive of treatment response.

Update on the Mechanism of Action of Aripiprazole: Translational Insights into Antipsychotic Strategies Beyond Dopamine Receptor Antagonism

Dopamine partial agonism and functional selectivity have been innovative strategies in the pharmacological treatment of schizophrenia and mood disorders and have shifted the concept of dopamine modulation beyond the established approach of dopamine D2 receptor (D2R) antagonism. Despite the fact that aripiprazole was introduced in therapy more than 12 years ago, many questions are still unresolved regarding the complexity of the effects of this agent on signal transduction and intracellular pathways, in part linked to its pleiotropic receptor profile. The complexity of the mechanism of action has progressively shifted the conceptualization of this agent from partial agonism to functional selectivity. From the induction of early genes to modulation of scaffolding proteins and activation of transcription factors, aripiprazole has been shown to affect multiple cellular pathways and several cortical and subcortical neurotransmitter circuitries. Growing evidence shows that, beyond the consequences of D2R occupancy, aripiprazole has a unique neurobiology among available antipsychotics. The effect of chronic administration of aripiprazole on D2R affinity state and number has been especially highlighted, with relevant translational implications for long-term treatment of psychosis. The hypothesized effects of aripiprazole on cell-protective mechanisms and neurite growth, as well as the differential effects on intracellular pathways [i.e. extracellular signal-regulated kinase (ERK)] compared with full D2R antagonists, suggest further exploration of these targets by novel and future biased ligand compounds. This review aims to recapitulate the main neurobiological effects of aripiprazole and discuss the potential implications for upcoming improvements in schizophrenia therapy based on dopamine modulation beyond D2R antagonism.

Effect of valproate on the plasma concentrations of aripiprazole in bipolar patients

OBJECTIVE

There is very limited documentation available on the effects of valproate co-medication on the pharmacokinetics of aripiprazole in a naturalistic setting. The aim of the present study was to investigate the effect of co-medication with valproate on serum concentrations of aripiprazole in bipolar disorder patients in a clinical setting.

METHOD

Plasma samples of bipolar disorder patients (n = 69) on a stable dose of aripiprazole 20 mg/day were analyzed by a liquid chromatography-mass spectrometry method in a routine therapeutic drug monitoring setting. Therapeutic drug monitoring was done for the entire study group before and after valproate co-administration.

RESULTS

We observed a statistically significant difference between the aripiprazole monotherapy and aripiprazole-valproate combination with respect to total aripiprazole plasma levels (p < 0.01). However, no statistically significant differences were noted in aripiprazole levels between the first week and the second week of valproate co-administration.

CONCLUSION

In conclusion, concurrent treatment with valproate resulted in changes in the total aripiprazole plasma levels by 23%. But a lower total aripiprazole concentration during co-medication with valproate, caused by protein binding displacement, is reported being clinically insignificant in previous studies. The results from these studies are important in order to clarify clinical safety and efficacy.

Comparison of adjunctive use of aripiprazole with bupropion or selective serotonin reuptake inhibitors/serotonin-norepinephrine reuptake inhibitors: analysis of patients beginning adjunctive treatment in a 52-week, open-label study

Background

This post hoc analysis assessed the safety, tolerability and effectiveness of long-term treatment with aripiprazole adjunctive to either bupropion or selective serotonin reuptake inhibitors (SSRIs)/serotonin–norepinephrine reuptake inhibitors (SNRIs) in patients with major depressive disorder (MDD).

Methods

Data from de novo patients (did not participate in 2 previous studies) in a 52-week, open-label safety study of adjunctive aripiprazole after documented inadequate response to 1–4 antidepressant treatments (ADTs; SSRI, SNRI, or bupropion) were analyzed post hoc. Assessments included safety and tolerability, sexual functioning (Massachusetts General Hospital Sexual Functioning Inventory [MGH-SFI]) and Clinical Global Impressions–Severity (CGI-S).

Results

Forty-seven patients received bupropion plus aripiprazole and 245 received an SSRI/SNRI plus aripiprazole; 19 (40.4%) and 78 (31.8%), respectively, completed 52 weeks of treatment, and 46 and 242, respectively, received ≥1 dose of study medication (safety sample). Median time to discontinuation (any reason) was 184.0 days. Overall, 97.8% of patients in the bupropion group and 93.8% in the SSRI/SNRI group experienced ≥1 adverse event. The most common treatment-emergent adverse events were fatigue (26.1%) and somnolence (21.7%) with bupropion and fatigue (23.6%) and akathisia (23.6%) with an SSRI/SNRI. Mean change in body weight at week 52 (observed cases) was +3.1 kg for bupropion and +2.4 kg for an SSRI/SNRI. Treatment-emergent, potentially clinically relevant abnormalities in fasting glucose occurred in 8.3% of patients with bupropion and 17.4% with an SSRI/SNRI; for abnormalities in fasting total cholesterol, the incidence was 25.0% and 34.7%, respectively. Mean (SE) change from baseline in fasting glucose was 1.4 (1.9) mg/dL with bupropion and 2.7 (1.5) mg/dL with an SSRI/SNRI. Baseline MGH-SFI item scores indicated less severe impairment with bupropion versus an SSRI/SNRI; in both groups most MGH-SFI items exhibited improvement at week 52. Mean CGI-S improvement at week 52 (last observation carried forward) was -1.4 with bupropion and -1.5 with an SSRI/SNRI (efficacy sample).

Conclusions

There were no unexpected AEs with long-term adjunctive aripiprazole therapy when added to either bupropion or SSRIs/SNRIs, and symptom improvement was similar between ADT groups. Sexual functioning in patients with MDD on antidepressants was also modestly improved after adding aripiprazole.

Trial registration

ClinicalTrials.gov: NCT00095745 (November 9, 2004).

Functionally selective dopamine D₂, D₃ receptor partial agonists

Dopamine D2 receptor-promoted activation of Gα(o) over Gα(i) may increase synaptic plasticity and thereby might improve negative symptoms of schizophrenia. Heterocyclic dopamine surrogates comprising a pyrazolo[1,5-a]pyridine moiety were synthesized and investigated for their binding properties when low- to subnanomolar K(i) values were determined for D(2L), D(2S), and D3 receptors. Measurement of [(35)S]GTPγS incorporation at D(2S) coexpressed with G-protein subunits indicated significant bias for promotion of Gα(o1) over Gα(i2) coupling for several test compounds. Functionally selective D(2S) activation was most striking for the carbaldoxime 8b (Gα(o1), pEC50 = 8.87, E(max) = 65%; Gα(i2), pEC50 = 6.63, E(max) = 27%). In contrast, the investigated 1,4-disubstituted aromatic piperazines (1,4-DAPs) behaved as antagonists for β-arrestin-2 recruitment, implying significant ligand bias for G-protein activation over β-arrestin-2 recruitment at D(2S) receptors. Ligand efficacy and selectivity between D(2S) and D3 activation were strongly influenced by regiochemistry and the nature of functional groups attached to the pyrazolo[1,5-a]pyridine moiety.

When to start aripiprazole therapy in patients with bipolar mania

Aripiprazole is a third generation atypical antipsychotic with compelling evidence as a highly effective treatment option in the management of acute manic and mixed episodes of bipolar I disorders. It has a unique mode of action, acting as a partial agonist at dopamine D2 and D3, and serotonin 5-HT1A; and exhibiting antagonistic action at the 5-HT2A and H1 receptors. Overall, it has a favorable safety and tolerability profile, with low potential for clinically significant weight gain and metabolic effects, especially compared to other well-established treatments. It also has a superior tolerability profile when used as maintenance treatment. Side effects like headache, insomnia, and extrapyramidal side effects (EPSEs), such as tremor and akathisia may be treatment limiting in some cases. It is efficacious in both acute mania and mixed states, and in the long-term prevention of manic relapses. Aripiprazole therefore, is a significant player in the current portfolio of anti-manic pharmacological treatments. The data sources for this article are from EMBASE, MEDLINE, and the clinical trial database searches for all the literature published between January 2003 and September 2013. The key search terms were "aripiprazole" combined with "bipolar disorder", "mania", "antipsychotics", "mood stabilizer", "randomized controlled trial", and "pharmacology". Abstracts and proceedings from national and international psychiatric meetings were also reviewed, along with reviews of the reference lists of relevant articles.

Effect of aripiprazole on cognitive function and hyperprolactinemia in patients with schizophrenia treated with risperidone

Objective

This study aimed to assess the efficacy of aripiprazole for the management of cognitive impairments and hyperprolactinemia in patients with schizophrenia on a stable dose of risperidone.

Methods

Thirty-five subjects stabilized on risperidone (3-6 mg/day) for a minimum of 3 months were enrolled in a double-blind, placebo-controlled phase for 12 weeks and an open-label phase for another 12 weeks. Subjects were randomly assigned to receive 10 mg/day aripiprazole (n=17) or placebo (n=18). Over the following 12 weeks, the the aripiprazole group received a flexible dose of aripiprazole while tapering risperidone. At baseline, week 12, and week 24, subjects were evaluated using the Positive and Negative Syndrome Scale (PANSS), Extrapyramidal Syndrome Rating Scale (ESRS), and standardized neuropsychological assessments. Serum prolactin levels were checked at baseline, week 1, week 2, and week 24.

Results

The mean change in total PANSS and cognitive function test scores between baseline and endpoint were similar in the aripiprazole and placebo groups. Scores on the ESRS and negative subscale of PANSS differed significantly between groups in both phases of the study (p<0.05), indicating a positive effect of aripiprazole. Compared with placebo, aripiprazole significantly reduced mean baseline serum prolactin levels within 1 week (p=0.015).

Conclusion

Adjunctive treatment with and switching to aripiprazole were not associated with improved cognitive function in patients with schizophrenia receiving risperidone; however, aripiprazole treatment decreased negative symptoms and risperidone-induced motor side effects and lowered serum prolactin levels.

Dopamine D3 and 5-HT1B receptor dysregulation as a result of psychostimulant intake and forced abstinence: Implications for medications development

Addiction to psychostimulants, including cocaine and amphetamine, is associated with dysregulation of dopamine and serotonin (5-HT) neurotransmitter systems. Neuroadaptations in these systems vary depending on the stage of the drug taking-abstinence-relapse cycle. Consequently, the effects of potential treatments that target these systems may vary depending on whether they are given during abstinence or relapse. In this review, we discuss evidence that dopamine D3 receptors (D3Rs) and 5-HT1B receptors (5-HT1BRs) are dysregulated in response to both chronic psychostimulant use and subsequent abstinence. We then review findings from preclinical self-administration models which support targeting D3Rs and 5-HT1BRs as potential medications for psychostimulant dependence. Potential side effects of the treatments are discussed and attention is given to studies reporting positive treatment outcomes that depend on: 1) whether testing occurs during self-administration versus abstinence, 2) whether escalation of drug self-administration has occurred, 3) whether the treatments are given repeatedly, and 4) whether social factors influence treatment outcomes. We conclude that D3/D2 agonists may decrease psychostimulant intake; however, side effects of D3/D2R full agonists may limit their therapeutic potential, whereas D3/D2R partial agonists have fewer undesirable side effects. D3-selective antagonists may not reduce psychostimulant intake during relapse, but nonetheless, may decrease motivation for seeking psychostimulants with relatively few side-effects. 5-HT1BR agonists provide a striking example of treatment outcomes that are dependent on the stage of the addiction cycle. Specifically, these agonists initially increase cocaine's reinforcing effects during maintenance of self-administration, but after a period of abstinence they reduce psychostimulant seeking and the resumption of self-administration. In conclusion, we suggest that factors contributing to dysregulation of monoamine systems, including drug history, abstinence, and social context, should be considered when evaluating potential treatments to better model treatment effects in humans. This article is part of a Special Issue entitled 'NIDA 40th Anniversary Issue'.

Early antipsychotic response to aripiprazole in adolescents with schizophrenia: predictive value for clinical outcomes

OBJECTIVE

In adults with chronic schizophrenia, most symptom decreases occur in the first few weeks of antipsychotic treatment, and nonresponse at week 2 predicts a later nonresponse. The trajectory of antipsychotic response and the predictive value of early antipsychotic effects were investigated for ultimate outcome in adolescent schizophrenia, where such data are still lacking.

METHOD

This post hoc analysis of a 6-week, randomized, double-blinded trial of aripiprazole (n = 196) versus placebo (n = 98) evaluated if adolescents 13 to 17 years old with schizophrenia exhibited substantial symptomatic improvement to aripiprazole in the first few treatment weeks and whether early response (ER) versus early nonresponse (ENR) predicted clinically relevant outcomes. ER decreased at least 20% and ENR decreased less than 20% in Positive and Negative Syndrome Scale (PANSS) total score at week 2 (ER2/ENR2) or 3 (ER3/ENR3). Ultimate response decreased at least 40% in PANSS score.

RESULTS

Nearly 50% of the PANSS decrease was achieved by week 2 and up to 75% by week 3. ER2/ER3 subjects showed significantly greater improvement than ENR subjects in PANSS total score, PANSS positive and negative subscale scores, and functionally relevant outcomes. In general, ER3 had better sensitivity, specificity, and positive and negative predictive values than ER2 for predicting ultimate response. ER2 subjects were 8.8 times (95% confidence interval 4.0-19.4) and ER3 subjects were 8.6 times (95% confidence interval 4.5-16.6) more likely to achieve remission at week 6 (p < .0001) than ENR2 and ENR3 subjects, respectively, although adverse events were similar.

CONCLUSIONS

Like adults with chronic schizophrenia, adolescents with early-phase schizophrenia exhibited most symptomatic improvement early during aripiprazole treatment, with week 3 improvements having the best predictive power. Although requiring extension, these results may inform clinical decision making. Clinical trial registration information-Aripiprazole in Adolescents with Schizophrenia, http://clinicaltrials.gov/, NCT00102063.

A UK panel consensus on the initiation of aripiprazole for the treatment of bipolar mania

OBJECTIVE

The objective of this consensus paper is to provide practical guidance on why and how aripiprazole, with its distinct pharmacological and side effect profile, should be used for treatment of acute bipolar mania.

METHODS

An advisory panel of UK healthcare professionals, with extensive experience of prescribing aripiprazole for acute bipolar mania, met to discuss its use in this setting.

RESULTS

The panel agreed that aripiprazole is effective in treating bipolar mania when prescribed and dosed appropriately, in both the short and long term, as monotherapy or in combination with a mood stabilizer. Unlike other atypical agents, aripiprazole has antimanic effects that are not associated with sedation, which is beneficial for patients, particularly in the long term. If rapid tranquillization is required when initiating aripiprazole in acutely disturbed patients, short-term coprescription of a benzodiazepine is recommended. Most side effects associated with aripiprazole occur within the first 1-3 weeks and are usually transient and easily treatable. Aripiprazole poses low risk of metabolic side effects, sexual dysfunction, and anhedonia, which can facilitate treatment adherence and help improve clinical outcomes.

CONCLUSIONS

Aripiprazole is an effective first-line treatment for acute bipolar mania with a favorable safety/tolerability profile.

Efficacy of adjunctive aripiprazole in major depressive disorder: a pooled response quartile analysis and the predictive value of week 2 early response

OBJECTIVE

To assess varying levels of response to aripiprazole adjunctive to standard antidepressant therapy (ADT) and the predictive value of an early response for a sustained response.

METHOD

This post hoc analysis of 3 similarly designed randomized, double-blind, placebo-controlled phase 3 studies investigated the efficacy and safety of adjunctive aripiprazole to standard ADT in patients with major depressive disorder (DSM-IV-TR criteria) who had a prior inadequate response to 1-3 ADTs (CN138-139 [September 2004-December 2006], CN138-163 [June 2004-April 2006], and CN138-165 [March 2005-April 2008]). Response levels were defined as percent decreases from baseline in Montgomery-Asberg Depression Rating Scale (MADRS) total score after 6 weeks of treatment, with a ≤ 25% decrease for minimal, > 25 to < 50% decrease for partial, ≥ 50% to < 75% decrease for moderate, and ≥ 75% decrease for a robust response to treatment.

RESULTS

More patients receiving adjunctive aripiprazole exhibited a partial (23.9% vs 17.9%, P = .017), moderate (23.1% vs 15.0%, P < .001), and robust response (14.3% vs 7.4%, P < .001) compared with adjunctive placebo. Adjunctive aripiprazole treatment compared with adjunctive placebo treatment was associated with a significantly greater proportion of patients achieving an early response (week 2, ≥ 50% reduction in MADRS total score, n = 110/539 vs n = 47/525, P < .001, number needed to treat = 9) and an endpoint response (relative risk = 1.7, 95% CI = 1.4-2.0, P < .001, number needed to treat = 7). A univariate logistic regression analysis revealed that an early response was a significant predictor of endpoint remission (P < .001).

CONCLUSIONS

Aripiprazole augmentation was associated with a significantly greater proportion of patients achieving a partial, moderate, or robust response to treatment compared with ADT alone. Patients showing an early response (week 2) to augmentation maintained their response through endpoint, suggesting that clinicians may make clinically meaningful decisions early during treatment.

TRIAL REGISTRATION

ClinicalTrials.gov identifiers: NCT00095823, NCT00095758, and NCT00105196.

Receptor targets for antidepressant therapy in bipolar disorder: an overview

The treatment of bipolar depression is one of the most challenging issues in contemporary psychiatry. Currently only quetiapine and the olanzapine-fluoxetine combination are officially approved by the FDA against this condition. The neurobiology of bipolar depression and the possible targets of bipolar antidepressant therapy remain relatively elusive. We performed a complete and systematic review to identify agents with definite positive or negative results concerning efficacy followed by a second systematic review to identify the pharmacodynamic properties of these agents. The comparison of properties suggests that the stronger predictors for antidepressant efficacy in bipolar depression were norepinephrine alpha-1, dopamine D1 and histamine antagonism, followed by 5-HT2A, muscarinic and dopamine D2 and D3 antagonism and eventually by norepinephrine reuptake inhibition and 5HT-1A agonism. Serotonin reuptake which constitutes the cornerstone in unipolar depression treatment does not seem to play a significant role for bipolar depression. Our exhaustive review is compatible with a complex model with multiple levels of interaction between the major neurotransmitter systems without a single target being either necessary or sufficient to elicit the antidepressant effect in bipolar depression.

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

Aripiprazole (Abilify®) is an atypical antipsychotic indicated for the treatment of mania associated with bipolar I disorder. It is unique in its class, as it is a partial agonist of dopamine D(2) and D(3), and serotonin 5-HT(1A) receptors and a modest antagonist of 5-HT(2A) receptors. This article reviews the pharmacological properties, clinical efficacy and tolerability of oral aripiprazole in the management of mania associated with bipolar I disorder in adults. In well designed clinical trials in patients with recent manic or mixed episodes associated with bipolar I disorder, oral aripiprazole monotherapy or adjunctive therapy to lithium or valproate improved symptoms of mania following short-term (≤12 weeks) or maintenance (≤100 weeks) treatment. In addition, maintenance treatment with aripiprazole (as monotherapy or adjunctive therapy) prevented the recurrence of any mood episodes or manic episodes (but not depressive episodes) in patients who had previously been stabilized and maintained on aripiprazole. Aripiprazole was generally well tolerated in these studies and was associated with a low risk of prolactin elevation, corrected QT interval prolongation and metabolic disturbances. Extrapyramidal symptoms occurred in up to 28% of aripiprazole recipients, but after longer-term treatment (≤100 weeks), symptom severity did not differ significantly from that in placebo recipients. Aripiprazole treatment generally did not increase bodyweight to a clinically relevant extent; however, more patients receiving aripiprazole monotherapy than placebo had clinically significant bodyweight gain during 100 weeks' treatment. Additionally, in a comparative trial, aripiprazole monotherapy was at least as effective as haloperidol monotherapy in terms of improving symptoms of mania, but had the advantage of a lower incidence of some adverse events, such as extrapyramidal symptom-related adverse events. Further trials comparing aripiprazole with other agents, including atypical antipsychotics, would help to definitively position aripiprazole relative to these agents. Current guidelines recommend aripiprazole as a first-line option (as monotherapy or adjunctive therapy) for the short-term treatment of mania associated with bipolar I disorder, and as a first-line (as monotherapy) or second-line (as adjunctive therapy) option for preventing the recurrence of mood episodes during longer-term therapy.

Aripiprazole in combination with lamotrigine for the long-term treatment of patients with bipolar I disorder (manic or mixed): a randomized, multicenter, double-blind study (CN138-392)

OBJECTIVES

To evaluate the efficacy and safety of aripiprazole (ARI) plus lamotrigine (LTG) compared with placebo (PBO) plus LTG, for long-term treatment in bipolar I disorder patients with a recent manic/mixed episode.

METHODS

After a 9-24 week stabilization phase receiving single-blind ARI (10-30 mg/day) plus open-label LTG (100 or 200 mg/day), patients maintaining stability (Young Mania Rating Scale/Montgomery-Åsberg Depression Rating Scale total scores ≤ 12) with ARI+LTG for eight consecutive weeks were randomized to continue on double-blind ARI + LTG or to receive PBO + LTG, after removing ARI from ARI + LTG treatment, and followed up for 52 weeks. The primary outcome measure was time from randomization to relapse into a manic/mixed episode.

RESULTS

 A total of 787 patients entered the stabilization phase, and 351 were randomized to ARI + LTG (n = 178) or PBO + LTG (n = 173). ARI + LTG yielded a numerically longer time to manic/mixed relapse than PBO + LTG, but it was not statistically significant [hazard ratio (HR) = 0.55; 95% confidence interval (CI): 0.30-1.03; p = 0.058]. The estimated relapse rates at Week 52 were 11% for ARI + LTG and 23% for PBO + LTG, yielding a number needed-to-treat of nine (95% CI: 5-121). The three most common adverse events were akathisia [10.8%, 6.1% for ARI + LTG and PBO + LTG, respectively; number needed-to-harm (NNH) = 22], insomnia (7.4%, 11.5%), and anxiety (7.4%, 3.6%). Mean weight change was 0.43 kg and -1.81 kg, respectively (last observation carried forward, p = 0.001). Rates of ≥ 7% weight gain with ARI + LTG and PBO + LTG were 11.9% and 3.5%, respectively (NNH = 12).

CONCLUSIONS

 ARI + LTG delayed the time to manic/mixed relapse but did not reach statistical significance. Safety and tolerability results revealed no unexpected adverse events for ARI combination with LTG.

Partial agonists in schizophrenia--why some work and others do not: insights from preclinical animal models

While dopamine D2 receptor partial agonists (PAs) have been long considered for treating schizophrenia, only one, aripiprazole, is clinically available for therapeutic use. This raises critically important questions as to what is unique about aripiprazole and to what extent animal models can predict therapeutic success. A number of PAs whose clinical fate is known: aripiprazole, preclamol, terguride, OPC-4392 and bifeprunox were compared to haloperidol (a reference antipsychotic) in several convergent preclinical animal models; i.e. amphetamine-induced locomotion (AIL) and conditioned avoidance response (CAR), predictive of antipsychotic effects; unilateral nigrostriatal lesioned rats, a model of hypo-dopaminergia; striatal Fos induction, a molecular marker for antipsychotic activity; and side-effects common to this class of drugs: catalepsy (motor side-effects) and prolactaemia. The results were compared across drugs with reference to their measured striatal D2 receptor occupancy. All the PAs occupied striatal D2 receptors in a dose dependent manner, inhibited AIL and CAR, and lacked motor side-effects or prolactinaemia despite D2 receptor occupancy exceeding 80%. At comparative doses, aripiprazole distinguished itself from the other PAs by causing the least rotation in the hypo-dopaminergic model (indicating the least intrinsic activity) and showed the highest Fos expression in the nucleus accumbens (indicating functional D2 antagonism). Although a number of PAs are active in antipsychotic animal models, not all of them succeed. Given that only aripiprazole is clinically available, it can be inferred that low functional intrinsic activity coupled with sufficient functional antagonism as reflected in the animal models may be a marker of success.

Young mania rating scale line item analysis in pediatric subjects with bipolar I disorder treated with aripiprazole in a short-term, double-blind, randomized study

OBJECTIVE

The aim of this study was to evaluate the effects of aripiprazole treatment on individual Young Mania Rating Scale (YMRS) line items in pediatric subjects with manic or mixed episodes associated with bipolar I disorder to better understand the discrete symptom improvements.

METHODS

This was a post hoc analysis of the YMRS line item data from a 4-week, multicenter, randomized, double-blind, placebo-controlled study. Two hundred ninety-six eligible subjects were randomized to aripiprazole 10 mg/day (n = 98), aripiprazole 30 mg/day (n = 99), or placebo (n = 99). The primary endpoint was the mean change in YMRS total scores from baseline to week 4. Effect sizes and treatment effect on individual line items were calculated.

RESULTS

Of the 296 subjects, 237 (80.1%) completed the 4-week study. Seven of the 11 YMRS line items showed a statistically significant improvement in both aripiprazole treatment groups versus placebo. Using the data for the pooled doses, the three YMRS line items with the greatest effect size at week 4 were irritability (effect size = 0.7; treatment effect = 1.43; p < 0.001), aggressive behavior (effect size = 0.7; treatment effect = 1.38; p < 0.001), and increased motor activity/energy (effect size = 0.6; treatment effect = 0.86; p < 0.001).

CONCLUSION

Aripiprazole improved a broad spectrum of symptoms across the YMRS scale.

In vitro pharmacology of aripiprazole, its metabolite and experimental dopamine partial agonists at human dopamine D2 and D3 receptors

Aripiprazole is the first dopamine D(2)/D(3) receptor partial agonist successfully developed and ultimately approved for treatment of a broad spectrum of psychiatric and neurological disorders. Aripiprazole's dopamine D(2) and serotonin 5-HT(1A) receptor partial agonist activities have been postulated to confer clinical efficacy without marked sedation, and a relatively favorable overall side-effect profile. Using aripiprazole's unique profile as a benchmark for new dopamine partial agonist development may facilitate discovery of new antipsychotics. We conducted an in vitro comparative analysis between aripiprazole, and its human metabolite OPC-14857 (7-(4-[4-(2,3-dichlorophenyl)-1-piperazinyl)butoxy)-2(1H)-quinolinone)); RGH-188 (trans-1-[4-[2-[4-(2,3-dichlorophenyl)piperazine-1-yl]ethyl]cyclohexyl]-3,3-dimethylurea), and its metabolite didesmethyl-RGH-188 (DDM-RGH-188); as well as bifeprunox, sarizotan, N-desmethylclozapine (NDMC; clozapine metabolite), and SDZ 208-912 (N-[(8α)-2-chloro-6-methylergolin-8-yl]-2,2-dimethylpropanamide). In vitro pharmacological assessment included inhibition of forskolin-stimulated cAMP accumulation and the reversal of dopamine-induced inhibition in clonal Chinese hamster ovary cell lines expressing D(2S), D(2L), D(3) Ser-9 and D(3) Gly-9 for human dopamine receptors. All test compounds behaved as dopamine D(2)/D(3) receptor partial agonists. Aripiprazole's intrinsic activity at dopamine D(2S) and D(2L) receptors was similar to that of OPC-14857 and RGH-188; lower than that of dopamine and bifeprunox; and higher than that of DDM-RGH-188, SDZ 208-912, sarizotan, and NDMC. Aripiprazole's intrinsic activity at dopamine D(3) Ser-9 and D(3) Gly-9 receptors was similar to that of OPC-14857 and sarizotan; lower than that of dopamine, bifeprunox, RGH-188 and DDM-RGH-188; and higher than that of SDZ 208-912 and NDMC. A consolidated assessment of these findings may help defining the most appropriate magnitude of intrinsic activity at dopamine D(2)/D(3) receptors for clinical efficacy and safety.

Functional potencies of dopamine agonists and antagonists at human dopamine D₂ and D₃ receptors

We measured the functional agonist potencies of dopamine agonists including antiparkinson drugs, and functional antagonist potencies of antipsychotics at human dopamine D(2) and D(3) receptors. In vitro pharmacological assessment included inhibition of forskolin-stimulated cAMP accumulation and the reversal of dopamine-induced inhibition in clonal Chinese hamster ovary cells expressing low and high densities of human dopamine D(2L) and D(2S) receptors (hD(2L)-Low, hD(2L)-High, hD(2S)-Low and hD(2S)-High, respectively) and human dopamine D(3) Ser-9 and D(3) Gly-9 receptors (hD(3)-Ser-9 and hD(3)-Gly-9, respectively). Cabergoline, bromocriptine, pergolide, (±)-7-hydroxy-N,N-di-n-propyl-2-aminotetralin (7-OH-DPAT), talipexole, pramipexole, R-(+)-trans-3,4,4a,10b-tetrahydro-4-propyl-2H,5H-[1]benzopyrano[4,3-b]-1,4-oxazin-9-olhydrochloride (PD128907) and ropinirole behaved as dopamine D(2) and D(3) receptor full agonists and showed higher potencies in hD(2L)-High and hD(2S)-High compared to hD(2L)-Low and hD(2S)-Low. In hD(3)-Ser-9 and hD(3)-Gly-9 compared to hD(2L)-Low and hD(2S)-Low, dopamine, ropinirole, PD128907, and pramipexole potencies were clearly higher; talipexole and 7-OH-DPAT showed slightly higher potencies; pergolide showed slightly lower potency; and, cabergoline and bromocriptine potencies were lower. Aripiprazole acted as an antagonist in hD(2L)-Low; a low intrinsic activity partial agonist in hD(2S)-Low; a moderate partial agonist in hD(3)-Ser-9 and hD(3)-Gly-9; a robust partial agonist in hD(2L)-High; and a full agonist in hD(2S)-High. Amisulpride, sulpiride and perphenazine behaved as preferential antagonists; and chlorpromazine and asenapine behaved as modest preferential antagonists; whereas fluphenazine, haloperidol, and blonanserin behaved as non-preferential antagonists in hD(2S)-Low and hD(2S)-High compared to hD(3)-Ser-9 and hD(3)-Gly-9. These findings may help to elucidate the basis of therapeutic benefit observed with these drugs, with varying mechanisms of action, in the treatment of Parkinson's disease, depression and schizophrenia.

Effectiveness of aripiprazole for medication overuse headache: a case report

Aripiprazole, a dopamine D2 receptor partial agonist, has been used to treat schizophrenia and might be effective for alcohol dependence and craving. We treated a 53-year-old woman with refractory medication overuse headache, which was successfully treated with aripiprazole. Our experience suggests that aripiprazole may be effective for patients with medication overuse headache.

Allostery at G protein-coupled receptor homo- and heteromers: uncharted pharmacological landscapes

For many years seven transmembrane domain G protein-coupled receptors (GPCRs) were thought to exist and function exclusively as monomeric units. However, evidence both from native cells and heterologous expression systems has demonstrated that GPCRs can both traffic and signal within higher-order complexes. As for other protein-protein interactions, conformational changes in one polypeptide, including those resulting from binding of pharmacological ligands, have the capacity to alter the conformation and therefore the response of the interacting protein(s), a process known as allosterism. For GPCRs, allosterism across homo- or heteromers, whether dimers or higher-order oligomers, represents an additional topographical landscape that must now be considered pharmacologically. Such effects may offer the opportunity for novel therapeutic approaches. Allosterism at GPCR heteromers is particularly exciting in that it offers additional scope to provide receptor subtype selectivity and tissue specificity as well as fine-tuning of receptor signal strength. Herein, we introduce the concept of allosterism at both GPCR homomers and heteromers and discuss the various questions that must be addressed before significant advances can be made in drug discovery at these GPCR complexes.

Effect of aripiprazole versus haloperidol on PANSS Prosocial items in early-episode patients with schizophrenia

BACKGROUND AND AIM

Improving social functioning is critically important in early-episode schizophrenia, if patients are to achieve functional recovery. This post-hoc, pooled analysis of two studies compared the effect of aripiprazole versus haloperidol on social functioning in early-episode schizophrenia.

METHODS

Data were pooled from two 52 week, randomized (2:1), double-blind, multicenter studies involving 1294 patients with chronic schizophrenia who were in an acute psychotic episode and had a history of positive antipsychotic response during previous episodes. The early-episode group was defined as patients who are <or=40 years of age with <or=5 years' duration of illness. Social functioning was assessed by mean change from baseline on the PANSS Prosocial subscale (ANCOVA and LOCF), comprising six PANSS items, and the Modified Prosocial subscale, comprising four PANSS items. Measurements were taken at approximately monthly intervals for up to 1 year.

RESULTS

Aripiprazole (n=237) demonstrated significant improvement versus haloperidol (n=123) as early as Week 18 on both the Prosocial subscale (-4.75 versus -3.78, p<0.05) and on the Modified Prosocial subscale (-3.16 versus -2.28, p<0.05). Patients receiving aripiprazole continued to show similar significant improvement versus haloperidol at all remaining timepoints through Week 52 using the Modified Prosocial subscale, but less consistent improvement with the Prosocial subscale. Significant advantage for the aripiprazole-treated patients was observed at Weeks 46 and 52 (endpoint) with both subscales.

CONCLUSION

In patients with early-episode schizophrenia, aripiprazole demonstrates greater improvement than haloperidol on PANSS items related to social functioning. The cognitive and functional implications of these findings remain to be clarified in future studies.

Assessment of safety, tolerability and effectiveness of adjunctive aripiprazole to lithium/valproate in bipolar mania: a 46-week, open-label extension following a 6-week double-blind study

OBJECTIVE

This study evaluated the long-term tolerability and effectiveness of aripiprazole adjunctive to lithium or valproate in partial responders with bipolar mania.

METHODS

Completers of a 6-week double-blind comparison of adjunctive aripiprazole versus placebo in bipolar mania partially responsive to lithium or valproate monotherapy could enter a 46-week extension treatment with open-label adjunctive aripiprazole plus lithium (ARI + LI) or valproate (ARI + VAL). Safety, efficacy and functioning were assessed.

CLINICAL TRIAL REGISTRATION

CN138-134LT: Study of Aripiprazole in Patients With Bipolar I Disorder; ID number: NCT00257972; registry: www.clinicaltrials.gov.

RESULTS

In total, 283 (ARI + LI n = 108; ARI + VAL n = 175) patients entered and 146 (ARI + LI n = 55; ARI + VAL n = 91) completed the 46-week, open-label extension. Frequently reported adverse events (AEs) that occurred with ARI + LI vs. ARI + VAL were: tremor (17.0% vs. 12.1%), akathisia (6.6% vs. 8.6%), headache (6.6% vs. 4.0%), insomnia (9.4% vs. 10.3%), depression (7.5% vs. 9.2%) and weight increase (11.3% vs. 8.6%). Extrapyramidal symptom-related AEs occurred in 24 (22.6%) ARI + LI- and 38 (21.8%) ARI + VAL-treated patients, with eight discontinuations. The majority of new-onset events of akathisia and insomnia occurred early. Mean (SE) weight change from double-blind endpoint to Week 46 (LOCF) was 2.3 (0.6) kg with ARI + LI and 2.0 (0.4) kg with ARI + VAL. Significant improvements from baseline over the 52 weeks (LOCF) occurred with ARI + LI and ARI + VAL on mean (95%CI) YMRS total score (-16.5 [-18.1; -14.8] and -17.6 [-18.9; -16.3], both p < 0.001 vs. baseline) and MADRS total score (-1.7 [-3.3; -0.1], p < 0.05 vs. baseline vs. -2.7 [-4.0; -1.4], p < 0.001 vs. baseline). Over the 46-week extension, continued aripiprazole provided continued YMRS improvement with ARI + LI (-2.9) and ARI + VAL (-3.3), while mean MADRS total changes were +1.1 and +1.0, respectively, and LIFE-RIFT changes were 0.2 and -0.5, respectively.

CONCLUSIONS

Long-term aripiprazole adjunctive to lithium/valproate in bipolar mania was safe and well tolerated. Improvements in manic symptoms and functioning were maintained. Aripiprazole, adjunctive to either lithium or valproate, appeared to be equally safe and effective combinations for the treatment of bipolar disorder.

LIMITATIONS

As an open-label extension study with a low completion rate, a conservative interpretation of the findings is warranted. Additionally, the study population was not randomly selected but chosen at the discretion of the investigator, and patients did not maintain therapeutic levels of their mood stabiliser consistently.

Changes in positive and negative syndrome scale-derived hostility factor in adolescents with schizophrenia treated with aripiprazole: post hoc analysis of randomized clinical trial data

INTRODUCTION

This post hoc analysis evaluated the effects of aripiprazole on Positive and Negative Syndrome Scale (PANSS) Hostility factor scores in adolescents with schizophrenia.

METHODS

In total, 302 adolescents (13-17 years) with schizophrenia were enrolled in a 6-week, multicenter, double-blind, randomized, placebo-controlled trial comparing aripiprazole (10 or 30 mg/day) with placebo. The PANSS was the primary outcome measure. To determine the effect of aripiprazole on hostility, a post hoc analysis of the PANSS Hostility factor and individual items was performed.

RESULTS

Aripiprazole was superior to placebo in reducing PANSS Hostility factor scores in adolescents with schizophrenia. After 6 weeks, aripiprazole 10 mg/day and aripiprazole 30 mg/day showed a statistically significant improvement versus placebo (-3.0, -3.7, versus -2.1; p < 0.05; last observation carried forward [LOCF]) in the PANSS Hostility factor. For aripiprazole 30 mg/day, statistically significant separation from placebo was evident from week 3 through week 6 and at week 6 for aripiprazole 10 mg/day. Individual PANSS Hostility, Uncooperativeness, and Poor Impulse Control Items showed statistically significant improvement with aripiprazole 30 mg/day over placebo at end point.

CONCLUSIONS

This post hoc analysis shows that aripiprazole (10 and 30 mg/day) is an effective treatment for hostility symptoms in adolescents with schizophrenia. Clinical trials information: ClinicalTrials.gov identifier: NCT00102063.

Cariprazine (RGH-188), a dopamine D(3) receptor-preferring, D(3)/D(2) dopamine receptor antagonist-partial agonist antipsychotic candidate: in vitro and neurochemical profile

Cariprazine {RGH-188; trans-N-[4-[2-[4-(2,3-dichlorophenyl)piperazin-1-yl]ethyl]cyclohexyl]-N',N'-dimethylurea hydrochloride}, a novel candidate antipsychotic, demonstrated approximately 10-fold higher affinity for human D(3) versus human D(2L) and human D(2S) receptors (pKi 10.07, 9.16, and 9.31, respectively). It displayed high affinity at human serotonin (5-HT) type 2B receptors (pK(i) 9.24) with pure antagonism. Cariprazine had lower affinity at human and rat hippocampal 5-HT(1A) receptors (pK(i) 8.59 and 8.34, respectively) and demonstrated low intrinsic efficacy. Cariprazine displayed low affinity at human 5-HT(2A) receptors (pK(i) 7.73). Moderate or low affinity for histamine H(1) and 5-HT(2C) receptors (pK(i) 7.63 and 6.87, respectively) suggest cariprazine's reduced propensity for adverse events related to these receptors. Cariprazine demonstrated different functional profiles at dopamine receptors depending on the assay system. It displayed D(2) and D(3) antagonism in [(35)S]GTPgammaS binding assays, but stimulated inositol phosphate (IP) production (pEC(50) 8.50, E(max) 30%) and antagonized (+/-)-quinpirole-induced IP accumulation (pK(b) 9.22) in murine cells expressing human D(2L) receptors. It had partial agonist activity (pEC(50) 8.58, E(max) 71%) by inhibiting cAMP accumulation in Chinese hamster ovary cells expressing human D(3) receptors and potently antagonized R(+)-2-dipropylamino-7-hydroxy-1,2,3,4-tetrahydronaphtalene HBr (7-OH-DPAT)-induced suppression of cAMP formation (pK(b) 9.57). In these functional assays, cariprazine showed similar (D(2)) or higher (D(3)) antagonist-partial agonist affinity and greater (3- to 10-fold) D(3) versus D(2) selectivity compared with aripiprazole. In in vivo turnover and biosynthesis experiments, cariprazine demonstrated D(2)-related partial agonist and antagonist properties, depending on actual dopaminergic tone. The antagonist-partial agonist properties of cariprazine at D(3) and D(2) receptors, with very high and preferential affinity to D(3) receptors, make it a candidate antipsychotic with a unique pharmacological profile among known antipsychotics.

Efficacy and safety of aripiprazole in the treatment of bipolar disorder: a systematic review

BACKGROUND

The current article is a systematic review concerning the efficacy and safety of aripiprazole in the treatment of bipolar disorder.

METHODS

A systematic Medline and repositories search concerning the usefulness of aripiprazole in bipolar disorder was performed, with the combination of the words 'aripiprazole' and 'bipolar'.

RESULTS

The search returned 184 articles and was last updated on 15 April 2009. An additional search included repositories of clinical trials and previous systematic reviews specifically in order to trace unpublished trials. There were seven placebo-controlled randomised controlled trials (RCTs), six with comparator studies and one with add-on studies. They assessed the usefulness of aripiprazole in acute mania, acute bipolar depression and during the maintenance phase in comparison to placebo, lithium or haloperidol.

CONCLUSION

Aripiprazole appears effective for the treatment and prophylaxis against mania. The data on bipolar depression are so far negative, however there is a need for further study at lower dosages. The most frequent adverse effects are extrapyramidal signs and symptoms, especially akathisia, without any significant weight gain, hyperprolactinaemia or laboratory test changes.

Time to psychiatric hospitalization in patients with bipolar disorder treated with a mood stabilizer and adjunctive atypical antipsychotics: a retrospective claims database analysis

OBJECTIVE

This study compared the time to psychiatric hospitalization in commercially insured patients with bipolar disorder who were treated with a mood stabilizer plus adjunctive aripiprazole versus adjunctive ziprasidone, olanzapine, quetiapine, or risperidone.

METHODS

This was a retrospective, propensity score-matched cohort study using the Ingenix I3/LabRx integrated insurance claims data set. Patients with bipolar disorder were included if they had >or=180 days of pre-index enrollment in the health plan without atypical antipsychotic exposure. Patients received mood stabilizers and subsequently received adjunctive atypical antipsychotic agents; they were then monitored for up to 90 days after the index antipsychotic prescription. The primary analysis was a Cox proportional hazards analysis to evaluate the time until psychiatric hospitalization comparing adjunctive aripiprazole with ziprasidone, olanzapine, quetiapine, or risperidone after adjusting for age, sex, and preindex hospitalization.

RESULTS

Adjunctive aripiprazole was associated with a longer time until hospitalization than adjunctive ziprasidone, olanzapine, quetiapine, or risperidone (hazard ratios 1.7, 1.6, 1.5, and 1.5, respectively; all, P < 0.05). Mean initial and maximum doses of all drugs were below those recommended by the package insert or clinical practice guidelines. Sensitivity analyses suggested the robustness of the results in the general population of patients with bipolar disorder recently treated with atypical antipsychotics.

CONCLUSIONS

This retrospective claims-data analysis suggests that in these adults with bipolar disorder treated with mood stabilizers, the addition of adjunctive aripiprazole was associated with a longer time to hospitalization than adjunctive ziprasidone, olanzapine, quetiapine, or risperidone during a 90-day follow-up period.

Bifeprunox and aripiprazole suppress in vivo VTA dopaminergic neuronal activity via D2 and not D3 dopamine autoreceptor activation

Bifeprunox and aripiprazole are two novel antipsychotics presenting partial agonistic activity for the D(2) and D(3) dopamine (DA) receptors. Using in vivo electrophysiological paradigms in anaesthetized rats, we have previously shown that both drugs independently inhibit the spontaneous firing and bursting activity of ventral tegmental area (VTA) dopaminergic neurons and partially reverse the suppressing effect of the full DA receptor agonist apomorphine. Moreover, we have also shown that the D(2/3) receptor antagonist haloperidol prevents the inhibitory effects of these antipsychotics, confirming their partial D(2)-like agonistic activities [L. Dahan, H. Husum, O. Mnie-Filali, J. Arnt, P. Hertel, N. Haddjeri, Effects of bifeprunox and aripiprazole on rat serotonin and dopamine neuronal activity and anxiolytic behaviour, J. Psychopharmacol. (2009)]. In the present electrophysiological study, selective antagonists of D(2) and D(3) receptors were used to further characterize the inhibitory role of bifeprunox and aripiprazole on the D(2) and D(3) receptors in vivo. Administration of bifeprunox (250 microg/kg, i.v.) or aripiprazole (300 microg/kg, i.v.) reduced the firing activity of VTA DA neurons by 40-50%. The bursting activity was reduced by 95% and 77% by bifeprunox and aripiprazole, respectively. Systemic administration of the preferential D(3) receptor antagonist GR218,231 (200 microg/kg, i.v.) did not modify the inhibitory effect of bifeprunox or aripiprazole, either on the firing or on the bursting activity. On the other hand, the preferential D(2) receptor antagonist L741,626 (500 microg/kg, i.v.) completely blocked the inhibitory effect of both bifeprunox and aripiprazole on the VTA DA neuronal activity. The present study shows that bifeprunox and aripiprazole behave as partial D(2), but not D(3), receptor agonists in vivo, inhibiting the firing activity (preferentially the phasic activity) of VTA DA cells.