Attenuation of anhedonia by cariprazine in the chronic mild stress model of depression

Adjunctive cariprazine for major depressive disorder: a systematic review and meta-analysis

Converging evidence has suggested that treatment augmentation with a second-generation atypical antipsychotic (SGA) may improve treatment outcomes in major depressive disorder (MDD) patients after an incomplete response to a first-line antidepressant. Cariprazine is a recently approved SGA for MDD augmentation. Herein, we evaluate both continuous (ie, change in depressive symptom severity scores over time) and categorical (ie, remission and response rates) outcomes. Following a full-text review, four randomized controlled trials (RCTs) were included in our meta-analysis, while five studies were included for a qualitative review. Risk ratios (RRs) were calculated for all included randomized controlled studies to determine the relative response and remission rates of cariprazine compared to placebo augmentation. The RR for all-cause dropout was also determined as a proxy for overall acceptability. Two studies found a statistically significant treatment response using cariprazine augmentation. One study observed depressive symptom remission for cariprazine compared to placebo. Our random-effects model revealed moderate antidepressant effects of cariprazine, with a standardized mean difference (SMD) in Montgomery-Åsberg Depression Rating Scale (MADRS) scores of -1.79 (95% CI): -2.89, -0.69). Our pooled response RR and remission RR were calculated as 1.21 (95% CI: 1.05, 1.39, P=0.008) and 0.99 (95% CI: 0.84, 1.17, P=0.91), respectively. The RR for response was statistically significant (P<0.05). However, the RR for remission was not statistically significant. The findings from our meta-analysis include a variable magnitude of effects. Evidence suggests cariprazine may be an effective treatment for MDD; however, further results are needed to clarify this relation.

The Differential Relation of Emotional, Physical, and Sexual Abuse Histories to Antidepressant Treatment Remission and Persistence of Anhedonia in Major Depression: A CAN-BIND-1 Report

OBJECTIVE

Childhood maltreatment is a potent enviromarker of risk for poor response to antidepressant medication (ADM). However, childhood maltreatment is a heterogeneous construct that includes distinct exposures that have distinct neurobiological and psychological correlates. The purpose of the current study is to examine the differential associations of emotional, physical, and sexual maltreatment to ADM outcome and to examine the unique role of anhedonia in driving poor response in patients with specific maltreatment histories.

METHODS

In a multicentre clinical trial of major depression, 164 individuals were assessed for childhood emotional, physical, and sexual maltreatment with a contextual interview with independent, standardized ratings. All individuals received 8 weeks of escitalopram, with nonresponders subsequently also receiving augmentation with aripiprazole, with outcomes measured with depression rating scales and an anhedonia scale.

RESULTS

Greater severity of emotional maltreatment perpetrated by the mother was a significant and direct predictor of lower odds of week 16 remission (odds ratio [OR] = 1.68, P = 0.02). In contrast, the relations of paternal-perpetrated emotional maltreatment and physical maltreatment to week 16 remission were indirect, mediated through greater severity of anhedonia at week 8.

CONCLUSIONS

We identify emotional maltreatment as a specific early exposure that places patients at the greatest risk for nonremission following pharmacological treatment. Further, we suggest that anhedonia is a key symptom domain driving nonremission in patients with particular maltreatment histories.

Effects of the atypical antipsychotic and D3/D2 dopamine partial agonist cariprazine on effort-based choice behavior: implications for modeling avolition

RATIONALE

Cariprazine is an atypical antipsychotic that acts as a D3/D2 receptor partial agonist. In addition to treating positive symptoms of schizophrenia, cariprazine may have utility for treating negative symptoms. Rodent studies have focused on the effects of cariprazine on cognitive functions and behaviors thought to be related to anhedonia. Avolition, which is characterized by reduced initiation and persistence of goal-directed behavior, is another important negative symptom.

OBJECTIVES

Effort-related choice tasks have been used as animal models of avolition. In these studies, cariprazine was assessed for its effects on effort-based choice in both rats and mice. Previous work has shown that D2 antagonists such as haloperidol and eticlopride produce a low-effort bias in rodents tested on effort-based choice tasks.

RESULTS

Low doses of cariprazine produced a low-effort bias in rats tested on the fixed ratio 5/chow feeding choice task, decreasing lever pressing for high carbohydrate pellets but increasing chow intake. Cariprazine did not alter preference or intake of these foods in free-feeding tests. The effort-related effects of cariprazine were reversed by co-administration of the adenosine A2A antagonist istradefylline, and cariprazine failed to reverse the effort-related effects of the dopamine-depleting agent tetrabenazine. In mouse touchscreen choice tests, low doses of cariprazine also produced a low-effort bias, shifting behavior away from panel pressing.

CONCLUSIONS

These results demonstrate that with these rodent models of avolition, cariprazine appears to act like a D2-family antagonist even at very low doses. Furthermore, the pharmacological regulation of avolition may differ from that of other negative symptoms.

Early effects of lurasidone treatment in a chronic mild stress model in male rats

RATIONALE

Stress represents a major contributor to the development of mental illness. Accordingly, exposure of adult rats to chronic stress represents a valuable tool to investigate the ability of a pharmacological intervention to counteract the adverse effects produced by stress exposure.

OBJECTIVES

The aim of this study was to perform a time course analysis of the treatment with the antipsychotic drug lurasidone in normalizing the anhedonic phenotype in the chronic mild stress (CMS) model in order to identify early mechanisms that may contribute to its therapeutic activity.

METHODS

Male Wistar rats were exposed to CMS or left undisturbed for 7 weeks. After two weeks of stress, both controls and CMS rats were randomly divided into two subgroups that received vehicle or lurasidone for five weeks. Weekly measures of sucrose intake were recorded to evaluate anhedonic behavior, and animals were sacrificed at different weeks of treatment for molecular analyses.

RESULTS

We found that CMS-induced anhedonia was progressively improved by lurasidone treatment. Interestingly, after two weeks of lurasidone treatment, 50% of the animals showed a full recovery of the phenotype, which was associated with increased activation of the prefrontal and recruitment of parvalbumin-positive cells that may lead to a restoration of excitatory/inhibitory balance.

CONCLUSION

These results suggest that the capacity of lurasidone to normalize anhedonia at an early stage of treatment may depend on its ability to modulate the function of the prefrontal cortex.

Models of Affective Illness: Chronic Mild Stress in the Rat

This article describes a chronic mild stress (CMS) model for predicting antidepressant response and investigating mechanisms of antidepressant action in rats. Following exposure to a variety of mild stressors for several weeks, the rats' behavior is modified in several ways that parallel symptoms of depression. Among these is a substantial reduction in consumption of a 1% sucrose solution, which models the cardinal symptom of major depression, anhedonia. Our standard procedure employs a battery of behavioral tests, comprising weekly assessment of sucrose intake and, at the end of treatment, the elevated plus-maze and novel object recognition tests to assess the anxiogenic and dyscognitive effects of CMS. Chronic administration of antidepressant drugs reverses the decreased sucrose intake and other behavioral changes in these subjects. Also effective are second-generation antipsychotics. The CMS model can be employed in discovery programs to identify anti-anhedonic drugs (e.g., antidepressants and antipsychotics) that act more quickly than existing agents. While most antidepressants require 3 to 5 weeks to normalize behavior, some treatments provide a faster onset of action. For example, the CMS-induced deficits can be reversed by acute or sub-chronic application of treatments that act rapidly in depressed patients, such as deep brain stimulation (DBS), ketamine, and scopolamine, as well as several compounds that have yet to be tested in humans but have fast-onset antidepressant-like effects in animals, such as the 5-HT-1A biased agonists NLX-101 and GLYX-13. Application of the CMS model in Wistar-Kyoto (WKY) rats causes similar behavioral changes to those seen in Wistars, but these are not reversed by antidepressant treatment. However, WKY rats respond to DBS and ketamine, which are effective in patients who are antidepressant non-responders, establishing CMS in WKY rats as a model of treatment-resistant depression. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Induction of chronic mild stress in rats as a model of depression and treatment-resistant depression.

Mini Review on Cariprazine: A Promising Antipsychotic Agent

Cariprazine is a piperazine derivative approved by the USFDA in 2015 as a novel atypical antipsychotic drug (APD) to treat adults with schizophrenia and bipolar manic or mixed episodes in adults. However, due to the partial agonist action on dopamine D₂, D₃ receptors, and serotonin 5-HT_1A receptors as well as the antagonist effect on 5-HT_2A, 5-HT_2B, and H₁ receptors, cariprazine differs pharmacologically from other APDs, both typical and atypical. Moreover, cariprazine also has a unique pharmacokinetic profile due to the formation of two clinically significant metabolites: desmethyl-cariprazine (DCAR) and desmethyl-cariprazine (DDCAR). They are eliminated by CYP3A4 and also, to a lesser extent, by CYP2D6. Here, we also review the effectiveness, safety, as well as current clinical update of cariprazine in bipolar I disorder associated with/without mania and schizophrenia through randomized and post-hoc analysis. The potential benefits of cariprazine as a promising therapeutic alternative in addressing major clinical requirements for better therapy of such severe neuropsychiatric conditions were demonstrated in this summarized review study.

Evaluation of the Effect of Cariprazine on Memory and Cognition in Experimental Rodent Models

The main symptoms of schizophrenia are categorized as positive, negative, and cognitive. Cognitive impairments do not generally respond to antipsychotics. Cariprazine is a novel antipsychotic conceived with the idea that high affinity for D3 receptors may elicit a favorable response in the management of cognitive deficits. We evaluated the pro-cognitive properties of 14-day long pre-treatment with cariprazine (0.25, 0.5, and 1 mg/kg b.w. intraperitoneally) in experimental rodent models with scopolamine-induced memory impairment employing novel object recognition test (NORT), T-maze, Y-maze, and passive avoidance tasks (step-through and step-down). Statistical analysis was performed with One Way ANOVA. In NORT cariprazine increased the recognition index. In T-maze and Y-maze cariprazine increased the working memory index as well as the percentage of spontaneous alternation. Cariprazine improved learning and memory in both short-term and long-term memory retention tests in step-down and step-through tasks. Cariprazine improves learning, recognition, and spatial memory in rats with scopolamine-induced memory impairment. Cariprazine's beneficial effect on cognition is likely due to its affinity for D3 receptors, as well as agonism at 5-HT1A receptors. Most probably, the cognitive-enhancing properties of cariprazine are the result of integrated modulation in the amygdala, hippocampus, and prefrontal cortex.

Exposure to chronic stress impairs the ability to cope with an acute challenge: Modulation by lurasidone treatment

Chronic stress represents a major contributor for the development of mental illness. This study aimed to investigate how animals exposed to chronic mild stress (CMS) responded to an acute stress (AS), as a vulnerability's challenge, and to establish the potential effects of the antipsychotic drug lurasidone on such mechanisms. Adult male Wistar rats were exposed or not (controls) to a CMS paradigm for 7 weeks. Starting from the end of week 2, animals were randomized to receive vehicle or lurasidone for 5 weeks. Sucrose intake was used to measure anhedonia. At the end, half of the animals were exposed to an acute stress before sacrifice. Exposure to CMS produced a significant reduction in sucrose consumption, whereas lurasidone progressively normalized such alteration. We found that exposure to AS produced an upregulation of Brain derived neurotrophic factor (Bdnf) in the prefrontal cortex of controls animals. This response was impaired in CMS rats and restored by lurasidone treatment. While in control animals, AS-induced increase of Bdnf mRNA levels was specific for Parvalbumin cells, CMS rats treated with lurasidone show a significant upregulation of Bdnf in pyramidal cells. Furthermore, when investigating the activation of different brain regions, CMS rats showed an impairment in the global response to the acute stressor, that was largely restored by lurasidone treatment. Our results suggest that lurasidone treatment in CMS rats may regulate specific circuits and mechanisms, which will ultimately contribute to boost resilience under stressful challenges.

Newer antipsychotics: Brexpiprazole, cariprazine, and lumateperone: A pledge or another unkept promise?

Antipsychotic agents are used for various indications in the treatment of psychiatric disorders. Despite their proven roles in multiple conditions, the treatment-emergent side effects of antipsychotic medications, such as metabolic side effects, are often the limiting factor for their long-term and short-term uses. Moreover, antipsychotic medications are often criticized for being less effective in treating different disabling symptoms such as negative symptoms of schizophrenia. As a result, the search for safer and more efficacious antipsychotic agents is ongoing. Newer antipsychotic agents are gaining attention related to emerging efficacy and tolerability data in treating neuropsychiatric conditions. In this review, we attempt to appraise the scientific data on psychopharmacology, safety profile, and efficacy of the newer additions to the list of second-generation antipsychotics, namely brexpiprazole, cariprazine, and lumateperone. We conducted a selective review utilizing PubMed, clinicaltrials.gov, and Cochrane databases to gather appropriate publications, keeping broad inclusion criteria. There were no restrictions on the age of the study population or the year of publication. We also cross-referenced articles and references to capture all existing studies. Our review of the current literature indicates that all three antipsychotic agents appear to be promising based on their short-term studies, while long-term studies remain limited. There is also a need for a head to head comparison between the newer antipsychotics with the other antipsychotic agents to ascertain if the newer agents are any better than the others.

Remission of persistent methamphetamine-induced psychosis after cariprazine therapy: presentation of a case report

In this case report, we described a patient admitted with persistent methamphetamine-induced psychotic symptoms, accompanied by negative symptoms, who appeared to respond to cariprazine treatment regarding his psychotic and craving symptoms. To our knowledge, no cariprazine-related data has been published about these type of patients. Our case suggests that cariprazine may improve both psychotic and addictive symptoms in subjects with persistent substance-induced psychotic disorders. Notably, our patient reported an abrupt decrease in substance craving and use, and an improvement in positive and negative psychotic symptoms. Although it is not possible to generalize the observations and findings gathered with this single case, it detected a potential effect of cariprazine on a drug naïve patient with persistent psychotic symptoms induced by methamphetamine for the first time.

Cariprazine modulates sleep architecture in rats

BACKGROUND

Cariprazine is a dopamine D₃-preferring D₃/D₂ receptor partial agonist compound recently introduced to treat schizophrenia and bipolar disorder. Although cariprazine is clinically classified as a low-somnolence drug, to date no detailed polysomnographic study is available on its effect on sleep.

AIMS

This study examined the acute systemic effects of cariprazine on the rat sleep architecture and electroencephalography spectral power.

METHODS

Sprague Dawley rats were recorded during their normal sleep period for four hours, and their sleep stages were classified.

RESULTS

Cariprazine (0.3 mg/kg i.p.) reduced the time spent in rapid eye movement (REM) sleep and increased REM latency. This dose of cariprazine decreased the gamma (40-80 Hz) band frequency oscillations and increased the theta (4-9 Hz) and alpha (9-15 Hz) frequencies during the wake periods but not during slow-wave sleep. The 0.03 mg/kg dose of cariprazine only increased the alpha power during the wake periods, while the 0.003 mg/kg dose was without any effect.

CONCLUSION

Taken together, the present results suggest that the REM-suppressing effect of cariprazine may be related to its effectiveness in improving depressive symptoms, as various drugs with similar REM-reducing properties effectively treat the depressive state, whereas the gamma power-reducing effect of cariprazine may be indicative of its efficacy in schizophrenia or mania, as similar effects have been observed with other D₂ and 5-HT₂ receptor antagonist drugs. These data contribute to our understanding of the complex mechanism of action that may stand behind the clinical efficacy of cariprazine.

Neuronal Dopamine D3 Receptors: Translational Implications for Preclinical Research and CNS Disorders

Dopamine (DA), as one of the major neurotransmitters in the central nervous system (CNS) and periphery, exerts its actions through five types of receptors which belong to two major subfamilies such as D1-like (i.e., D1 and D5 receptors) and D2-like (i.e., D2, D3 and D4) receptors. Dopamine D3 receptor (D3R) was cloned 30 years ago, and its distribution in the CNS and in the periphery, molecular structure, cellular signaling mechanisms have been largely explored. Involvement of D3Rs has been recognized in several CNS functions such as movement control, cognition, learning, reward, emotional regulation and social behavior. D3Rs have become a promising target of drug research and great efforts have been made to obtain high affinity ligands (selective agonists, partial agonists and antagonists) in order to elucidate D3R functions. There has been a strong drive behind the efforts to find drug-like compounds with high affinity and selectivity and various functionality for D3Rs in the hope that they would have potential treatment options in CNS diseases such as schizophrenia, drug abuse, Parkinson’s disease, depression, and restless leg syndrome. In this review, we provide an overview and update of the major aspects of research related to D3Rs: distribution in the CNS and periphery, signaling and molecular properties, the status of ligands available for D3R research (agonists, antagonists and partial agonists), behavioral functions of D3Rs, the role in neural networks, and we provide a summary on how the D3R-related drug research has been translated to human therapy.

Cariprazine as a therapeutic option for schizophrenia: a drug evaluation

Introduction: Schizophrenia is a very disabling condition that may result in a significant impairment of individual, professional, and social adjustments. Antipsychotics (APs), the first-line treatment for schizophrenia, in many cases modify the course of the disease, by reducing the institutionalization risk, at the price of severe and invalidating side effects. Cariprazine is one of the latest second-generation APs (SGAs) acting as a partial agonist of type 2 and 3 dopamine receptors, which was recently approved for the treatment of adult schizophrenia.Areas covered: The authors provide a critical review and commentary on the currently available data on the effectiveness and tolerability of cariprazine in schizophrenic patients, with a particular focus on its specific target symptoms.Expert opinion: Cariprazine appears significantly effective on both acute and maintenance treatment of schizophrenia, and in improving positive, negative, and cognitive symptoms, slightly more than other SGAs. It shows a good safety and tolerability profile, with akathisia being its most common side effect. Although further independent studies are needed to clarify its precise advantages over other SGAs, cariprazine seems a promising compound not only in schizophrenia, but also in a broad range of psychiatric conditions, including perhaps bipolar and addictive disorders.

Anti-Stress Properties of Atypical Antipsychotics

Stress exposure represents a major environmental risk factor for schizophrenia and other psychiatric disorders, as it plays a pivotal role in the etiology as well as in the manifestation of disease symptomatology. It may be inferred that pharmacological treatments must be able to modulate the behavioral, functional, and molecular alterations produced by stress exposure to achieve significant clinical outcomes. This review aims at examining existing clinical and preclinical evidence that supports the ability of atypical antipsychotic drugs (AAPDs) to modulate stress-related alterations. Indeed, while the pharmacodynamic differences between AAPDs have been extensively characterized, less is known on their ability to regulate downstream mechanisms that are critical for functional recovery and patient stabilization. We will discuss stress-related mechanisms, spanning from neuroendocrine function to inflammation and neuronal plasticity, which are relevant for the manifestation of schizophrenic symptomatology, and we will discuss if and how AAPDs may interfere with such mechanisms. Considering the impact of stress in everyday life, we believe that a better understanding of the potential effects of AAPDs on stress-related mechanisms may provide novel and important insights for improving therapeutic strategies aimed at promoting coping mechanisms and enhancing the quality of life of patients affected by psychiatric disorders.

Long-term administration of cariprazine increases locus coeruleus noradrenergic neurons activity and serotonin1A receptor neurotransmission in the hippocampus

BACKGROUND

Cariprazine, the novel dopamine (DA) D₃-preferring D₃/D₂ and serotonin (5-HT)_1A receptor partial agonist, has activity as an adjunctive therapy in major depressive disorder (MDD).

AIMS

This study aims to investigate the effects of chronic cariprazine administration in combination with the selective serotonin reuptake inhibitor escitalopram on the activity of monoaminergic systems.

METHODS

Rats received cariprazine alone and in adjunct to escitalopram for 2 and 14 days and the firing activity of dorsal raphe nucleus 5-HT, locus coeruleus norepinephrine (NE) and ventral tegmental area DA neurons was assessed. 5-HT and NE neurotransmission in hippocampus pyramidal neurons was evaluated by assessing tonic activation of their 5-HT_1A, and α₁- and α₂-adrenergic receptors, using their selective antagonists.

RESULTS

Two and 14-day cariprazine regimens increased the firing rate of NE, but not 5-HT and DA neurons. Addition of cariprazine to escitalopram reversed the inhibitory effect of escitalopram on NE but not 5-HT and DA neurons. In the hippocampus, there was an increase in neurotransmission at 5-HT_1A receptors in cariprazine-treated rats, but no change in overall NE transmission by either regimen.

CONCLUSION

Cariprazine increased NE neuronal firing and reversed the escitalopram-induced inhibition of these neurons. Despite a lack of effect on 5-HT neuronal firing activity, there was an increase in tonic activation of hippocampus 5-HT_1A receptors by cariprazine alone but not with the combination. These effects provide a possible rationale for the clinical efficacy of cariprazine as an adjunctive strategy in patients with MDD.

The role of dopamine D3 receptors in the mechanism of action of cariprazine

Cariprazine is a new atypical antipsychotic drug (APD) with a unique pharmacodynamic profile, different from both typical and atypical APDs. Specifically, cariprazine acts as a partial agonist at the dopamine (DA) D2 and D3 receptors and serotonin 5-HT1A receptors, and as an antagonist at the 5-HT2B receptors. Moreover, it shows moderate affinities for adrenergic, histaminergic, and cholinergic receptors that are involved in mediating the side effects characteristic of typical APDs. In this review, we discuss the contribution of DA D3 receptors (D3Rs) in the etiology and pathophysiology of schizophrenia and the potential benefits that may be associated with a more selective targeting of D3R by APDs, as compared to other dopaminergic and non-dopaminergic receptor subtypes. Cariprazine, by acting on D3Rs, ameliorates anhedonia and cognitive deficits in animal models based on environmental or pharmacological manipulation. The reviewed results support the potential benefits of cariprazine in treating negative symptoms and cognitive deficits of schizophrenia, and therefore representing a promising approach in addressing the unmet clinical needs for the improved treatment of this serious neuropsychiatric disorder.

Efficacy and safety of cariprazine in bipolar I depression: A double-blind, placebo-controlled phase 3 study

OBJECTIVE

To assess the efficacy, safety, and tolerability of cariprazine in the treatment of the depressed phase of bipolar I disorder in adults (NCT02670538).

METHODS

In this phase 3 double-blind placebo-controlled study, adult patients with bipolar I disorder according to the Diagnostic and Statistical Manual - 5th Edition criteria and a current depressive episode were randomized to placebo (n = 167), cariprazine 1.5 mg/day (n = 168) or cariprazine 3.0 mg/day (n = 158). Efficacy parameters were changes in the Montgomery-Åsberg Depression Rating Scale (MADRS) total scores (primary) and Clinical Global Impressions - Severity (CGI-S) scores (secondary) from baseline to Week 6 compared to placebo. A mixed-model for repeated measures was used to estimate the least-squares mean differences (LSMD); P-values were adjusted for multiplicity. Adverse events (AEs), laboratory results, vital signs, and suicide risk were monitored.

RESULTS

Cariprazine 1.5 mg/day significantly reduced depressive symptoms on the primary (MADRS LSMD = -2.5; adjusted P = .0417) and secondary (CGI-S LSMD = -0.3; adjusted P = .0417) efficacy parameters vs placebo; differences were not statistically significant for cariprazine 3.0 mg/day. Common treatment-emergent AEs (≥5% in either cariprazine group and at least twice the incidence of placebo) were akathisia, restlessness, nausea, and fatigue. Mean metabolic parameter changes were low and generally comparable among groups; mean weight increases were ≤0.5 kg for all groups.

CONCLUSIONS

Cariprazine 1.5 mg/day significantly reduced depressive symptoms in adults with bipolar I depression compared to placebo, but differences were not significant for cariprazine 3.0 mg/day. The safety and tolerability profiles were similar to previous studies of cariprazine.

Evaluation of cariprazine in the treatment of bipolar I and II depression: a randomized, double-blind, placebo-controlled, phase 2 trial

This double-blind placebo-controlled, fixed/flexible-dose phase 2 trial assessed the efficacy, safety, and tolerability of cariprazine vs. placebo for depressive episodes associated with bipolar I or II disorder. Primary endpoint was change in Montgomery-Åsberg Depression Rating Scale (MADRS) total scores (baseline to week 8), and secondary endpoint was mean Clinical Global Impressions-Improvement score (week 8). Patients were randomized (N = 233) 1:1:1 to placebo, 'low-dose' 0.25-0.5 mg/day or 'high-dose' 1.5-3.0 mg/day cariprazine. Adverse events, laboratory results, vital signs, extrapyramidal symptoms, and suicide risk were monitored. Neither cariprazine group significantly separated from placebo in primary (mixed-effect model repeated measures MADRS least-squares mean differences: low-dose = -0.7, P = 0.7408; high-dose = 0.0, P = 0.9961) or secondary efficacy measures. No new safety signals with cariprazine were observed and common treatment-emergent adverse events (≥5% of cariprazine patients and twice the rate of placebo) included insomnia, akathisia, dry mouth, nausea, weight increased, diarrhea, restlessness, vomiting, musculoskeletal stiffness, migraine, and cough. Metabolic and weight changes were generally similar for cariprazine and placebo. Factors that may have affected the outcome of the trial were identified, which helped to inform the design and conduct of subsequent phase 2b/3 clinical trials of cariprazine in bipolar depression.

Cariprazine as a treatment across the bipolar I spectrum from depression to mania: mechanism of action and review of clinical data

Cariprazine is one of the newest dopamine-serotonin partial agonists, also known as 'atypical' second generation antipsychotics. Originally approved for acute and maintenance treatment of schizophrenia as well as for acute mania and mixed mania/depression, cariprazine has now been approved for bipolar I depression. Additionally, post hoc analyses of bipolar I depressed subjects show that both those with and those without concurrent manic features were improved following treatment with cariprazine. Maintenance studies are in progress in bipolar disorder, as are studies to augment antidepressants in unipolar major depressive episodes insufficiently responsive to treatment. Here, we review specifically the efficacy and safety data of cariprazine in bipolar I disorder and discuss the hypothesized mechanism of action of cariprazine and how it could theoretically be linked to caprazine's broad therapeutic actions across the mood disorder spectrum.

Corticosterone Injection Impairs Follicular Development, Ovulation and Steroidogenesis Capacity in Mice Ovary

Simple Summary

Researchers have hitherto established hundreds of animal stress models. However, these models have some limitations due to the complexity in operation and large differences between individual animals. In particular, there are few stress models that are specifically applied in mammalian ovaries. In this study, using intraperitoneal injection of cortisol/corticosterone (CORT), we successfully established a stress model that acts on the ovarian function. Our data showed that CORT inhibits ovarian and follicular development and blocks ovulation. The establishment of this model might provide a living platform for studying ovarian stress in future research.

Abstract

The aim of this study is to establish an ovarian stress model, and to investigate the effects of stress on follicular development. Our data showed that continuous intraperitoneal injection of CORT successfully created a stressful environment in the ovary. To assess the effects of CORT on ovarian functions, 80 three-week-old ICR (Institute of Cancer Research) female mice were randomly divided into control group and treatment group. All mice were injected intraperitoneally with pregnant horse serum gonadotropin (PMSG). At the same time, the treatment group were injected with CORT (1 mg/mouse) at intervals of 8 h; while the control group was injected with same volume of methyl sulfoxide (DMSO). Blood, ovaries, or ovarian granulosa cell samples were collected at 24 h, 48 h, and 55 h after PMSG injection. The results showed that, compared with the control group, CORT-injected mice revealed a significant decrease in ovulation rates, ovarian weight, ovarian index, the number of secondary follicles and mature follicles, levels of estrogen and progesterone, and mRNA expression of steroid synthase-related genes. Collectively, our findings clearly demonstrated that CORT injection could represent an effective practice to simulate stresses that inhibit ovarian functions by reducing follicular development and ovulation.

Cariprazine for the treatment of bipolar mania with mixed features: A post hoc pooled analysis of 3 trials

BACKGROUND

When bipolar I disorder (BP-I) mania is accompanied by subsyndromal depressive symptoms, a more complicated illness presentation results. To qualify for the mixed features specifier during mania, the DSM-5 requires ≥3 "non-overlapping" depressive symptoms (DS); notwithstanding, concerns of this definition's ecological validity and implications for timely diagnosis remain.

METHODS

Herein, patients were pooled from three similarly-designed pivotal trials of cariprazine compared to placebo for BP-I mania (NCT00488618/NCT01058096/NCT01058668) in post hoc analyses of mixed features using three criteria: ≥3 DS (DSM-5), ≥2 DS, and Montgomery-Åsberg Depression Rating Scale (MADRS) total score ≥10. Efficacy of cariprazine compared to placebo was assessed (Week 3) by Young Mania Rating Scale (YMRS) and MADRS scores and rates of mania response and remission.

RESULTS

In pooled patients (N = 1037), cariprazine significantly improved mean YMRS scores compared to placebo for each criterion; LSMDs were ≥3 DS = -3.79 (P = .0248), ≥2 DS = -2.91 (P = .0207), and ≥10 MADRS = -5.49 (P < .0001). More cariprazine- than placebo-treated patients met YMRS response and remission criteria, reaching significance for response in ≥2 DS (34% versus 47%; number-needed-to-treat [NNT] = 8, P = .0483) and ≥10 MADRS (31% versus 57%, NNT = 4, P < .0001) and for remission in ≥2 DS (27% versus 39%, NNT = 9, P = .0462), ≥10 MADRS (23% versus 44%, NNT = 5, P < .0001). Depressive symptoms were improved compared to placebo, reaching statistical significance in the MADRS ≥10 subgroup (LSMD = -1.59, P = .0082).

LIMITATIONS

Post hoc analysis, MADRS  < 18 entry criterion may have prevented assessment of MADRS changes.

CONCLUSIONS

Cariprazine significantly reduced manic and depressive symptoms in patients with mixed features with differential efficacy across the subgroups analyzed herein.

Preclinical pharmacodynamic and pharmacokinetic characterization of the major metabolites of cariprazine

INTRODUCTION

Cariprazine, a dopamine D3-preferring D3/D2 receptor partial agonist and serotonin 5-HT1A receptor partial agonist, has two major human metabolites, desmethyl-cariprazine (DCAR) and didesmethyl-cariprazine (DDCAR). The metabolite pharmacology was profiled to understand the contribution to cariprazine efficacy.

METHODS

In vitro receptor binding and functional assays, electrophysiology, animal models, microdialysis, and kinetic-metabolism approaches were used to characterize the pharmacology of DCAR and DDCAR.

RESULTS

Similar to cariprazine, both metabolites showed high affinity for human D3, D2L, 5-HT1A, 5-HT2A, and 5-HT2B receptors, albeit with higher selectivity than cariprazine for D3 versus D2 receptors. In [35S]GTPγS binding assays, cariprazine and DDCAR were antagonists in membranes from rat striatum and from cells expressing human D2 and D3 receptors, and were partial agonists in membranes from rat hippocampus. In cAMP signaling assays, cariprazine, DCAR, and DDCAR acted as partial agonists at D2 and D3 receptors; cariprazine and DDCAR were full agonists, whereas DCAR was a partial agonist at 5-HT1A receptors. Cariprazine, DCAR, and DDCAR were pure antagonists at human 5-HT2B receptors. Cariprazine and DDCAR increased rat striatal dopamine and reduced cortical serotonin turnover. Cariprazine and DDCAR showed similar in vivo D3 receptor occupancy in rat brain; however, cariprazine was more potent for D2 receptor occupancy. Both cariprazine and DDCAR dose-dependently but partially suppressed the spontaneous activity of midbrain dopaminergic neurons in rats, with the parent compound being more potent but shorter acting than its metabolite. Consistent with the D2 receptor occupancy profile, DDCAR was 3- to 10-fold less potent than cariprazine in rodent models of antipsychotic-like activity. Following acute cariprazine administration, DDCAR was detected in the rodent brain but at much lower levels than cariprazine.

CONCLUSION

Overall, in vitro and in vivo pharmacological profiles of DCAR and DDCAR demonstrated high similarity with cariprazine, suggesting that the major metabolites of cariprazine contribute significantly to its clinical efficacy.

Cariprazine Treatment of Bipolar Depression: A Randomized Double-Blind Placebo-Controlled Phase 3 Study

OBJECTIVE

Cariprazine, a dopamine D₃/D₂ and 5-HT_1A receptor partial agonist, was found to be effective in treating bipolar I depression in a previous phase 2 study. This phase 3 study further assessed the efficacy, safety, and tolerability of cariprazine in bipolar I depression.

METHODS

In a double-blind placebo-controlled study, adult participants (18-65 years old) who met DSM-5 criteria for bipolar I disorder and a current depressive episode were randomly assigned to receive placebo (N=158) or cariprazine at 1.5 mg/day (N=157) or 3.0 mg/day (N=165). The primary and secondary efficacy parameters were changes from baseline to week 6 in Montgomery-Åsberg Depression Rating Scale (MADRS) score and Clinical Global Impressions severity (CGI-S) score, respectively. Least squares mean differences were estimated using a mixed model for repeated measures, and p values were adjusted for multiplicity.

RESULTS

Both dosages of cariprazine were significantly more effective than placebo in improving depressive symptoms (reducing MADRS total score); the least squares mean differences were -2.5 (95% CI=-4.6, -0.4) for cariprazine at 1.5 mg/day and -3.0 (95% CI=-5.1, -0.9) for cariprazine at 3.0 mg/day. Both cariprazine dosages were associated with lower CGI-S scores compared with placebo, but the differences did not reach statistical significance after adjustment for multiplicity (least squares mean difference, -0.2 [95% CI=-0.5, 0.0] for the 1.5 mg/day group and -0.3 [95% CI=-0.5, 0.0] for the 3.0 mg/day group). Common treatment-emergent adverse events (in at least 5% of participants in either cariprazine treatment group and twice the rate of the placebo group) were nausea, akathisia, dizziness, and sedation. Mean changes in weight and metabolic parameters were relatively small and comparable across groups.

CONCLUSIONS

Cariprazine, at both 1.5 mg/day and 3.0 mg/day, was effective, generally well tolerated, and relatively safe in reducing depressive symptoms in adults with bipolar I depression.

Cariprazine for the treatment of bipolar depression: a review

INTRODUCTION

Depressive symptoms and episodes dominate the course of bipolar disorder. The morbidity of bipolar disorder is disproportionately mediated by depressive symptoms; economic costs of bipolar disorder are also disproportionately due to unremitting depressive symptoms. Relatively few treatment options have established unequivocal efficacy in the treatment of bipolar depression. Herein we review evidence regarding the efficacy of the D₃ preferring D₂/D₃ partial agonist cariprazine in the treatment of adults with bipolar depression. Areas covered: Randomized controlled trials that sought to determine the efficacy, tolerability, and safety of cariprazine in adults with bipolar I depression. Expert opinion: The available evidence from clinical trials indicates that cariprazine is effective at treating bipolar depression wherein treatment for bipolar depression remains an unmet need in bipolar disorder. Cariprazine has demonstrated good tolerability and safety profiles in bipolar disorder. Furthermore, cariprazine may be effective in improving both anhedonia and cognitive dysfunction. Long term prevention studies in bipolar depression, as well as separate studies evaluating efficacy in adults with bipolar II depression, are needed.

Efficacy of cariprazine across symptom domains in patients with acute exacerbation of schizophrenia: Pooled analyses from 3 phase II/III studies

Schizophrenia affects various symptom domains, including positive and negative symptoms, mood, and cognition. Cariprazine, a dopamine D₃/D₂ receptor partial agonist and serotonin 5-HT_1A receptor partial agonist, with preferential binding to D₃ receptors, is approved for the treatment of adult patients with schizophrenia (US, Europe) and mania associated with bipolar I disorder (US). For these investigations, data were pooled from 3 positive, 6-week, double-blind, placebo-controlled, phase II/III trials of cariprazine in patients with acute exacerbation of schizophrenia (NCT00694707, NCT01104766, NCT01104779); 2 trials were fixed-dose and 1 trial was flexible-dose. Post hoc analyses evaluated mean change from baseline to week 6 in Positive and Negative Syndrome Scale (PANSS) -derived symptom factors (positive symptoms, negative symptoms, disorganized thought, uncontrolled hostility/excitement, anxiety/depression) and PANSS single items for cariprazine (1.5-9.0 mg/d) versus placebo. P values were not adjusted for multiple comparisons. At week 6, statistically significant differences versus placebo were seen for cariprazine on all 5 PANSS factors (P < 0.01 all). Effects sizes ranged from 0.21 (anxiety/depression) to 0.47 (disorganized thought). Dose-response analysis from the fixed-dose studies found significant differences for all cariprazine doses (1.5, 3.0, 4.5, and 6.0 mg/d) versus placebo in PANSS total score, and in negative symptom and disorganized thought factor scores (P < 0.001). Differences between cariprazine and placebo were also statistically significant on 26 of 30 PANSS single items (P < 0.05). In these post hoc analyses, cariprazine was effective versus placebo in improving all 5 PANSS factor domains, suggesting that it may have broad-spectrum efficacy in patients with acute schizophrenia.

International Union of Basic and Clinical Pharmacology CIV: The Neurobiology of Treatment-resistant Depression: From Antidepressant Classifications to Novel Pharmacological Targets

Major depressive disorder is one of the most prevalent and life-threatening forms of mental illnesses and a major cause of morbidity worldwide. Currently available antidepressants are effective for most patients, although around 30% are considered treatment resistant (TRD), a condition that is associated with a significant impairment of cognitive function and poor quality of life. In this respect, the identification of the molecular mechanisms contributing to TRD represents an essential step for the design of novel and more efficacious drugs able to modify the clinical course of this disorder and increase remission rates in clinical practice. New insights into the neurobiology of TRD have shed light on the role of a number of different mechanisms, including the glutamatergic system, immune/inflammatory systems, neurotrophin function, and epigenetics. Advances in drug discovery processes in TRD have also influenced the classification of antidepressant drugs and novel classifications are available, such as the neuroscience-based nomenclature that can incorporate such advances in drug development for TRD. This review aims to provide an up-to-date description of key mechanisms in TRD and describe current therapeutic strategies for TRD before examining novel approaches that may ultimately address important neurobiological mechanisms not targeted by currently available antidepressants. All in all, we suggest that drug targeting different neurobiological systems should be able to restore normal function but must also promote resilience to reduce the long-term vulnerability to recurrent depressive episodes.

Efficacy of adjunctive low-dose cariprazine in major depressive disorder: a randomized, double-blind, placebo-controlled trial

This 19-week, double-blind, placebo-controlled, randomized phase 2 study evaluated the efficacy, safety, and tolerability of adjunctive cariprazine (0.1-0.3 and 1.0-2.0 mg/day) as an antidepressant treatment for adults with treatment-resistant major depressive disorder (MDD) (NCT00854100). The primary endpoint was change in the Montgomery-Åsberg Depression Rating Scale (MADRS) total score and the secondary was change in the Clinical Global Impression-Intensity score. Additional efficacy parameters were also assessed. A total of 231 patients were randomized. None of the predefined parameters reached significance for either cariprazine doses, but higher doses yielded numerically greater mean changes in MADRS and Clinical Global Impression-Intensity scores, and MADRS response and remission rates, compared with placebo. No differences were seen on any measures between cariprazine 0.1-0.3 mg/day and placebo. Cariprazine was relatively well tolerated, and common treatment-emergent adverse events (incidence ≥5% and twice the placebo group rate) in both dosage groups included headache, arthralgia, restlessness, fatigue, increased appetite, insomnia, dry mouth, and constipation. In conclusion, both cariprazine doses were relatively well tolerated; although differences were not statistically significant, patients treated with cariprazine 1.0-2.0 mg/day had greater mean decreases in measures of depression symptoms compared with placebo, which is consistent with another adjunctive cariprazine MDD study, and thus warrants further investigation.

Cariprazine for acute and maintenance treatment of adults with schizophrenia: an evidence-based review and place in therapy

Cariprazine is an oral antipsychotic approved in the US and EU for the treatment of schizophrenia. Cariprazine differs from other antipsychotics in that it is a dopamine D3- and D2-receptor partial agonist, with tenfold higher affinity for D3 receptors than for D2 receptors. Cariprazine is metabolized in two steps by CYP3A4 to didesmethyl-cariprazine (DDCAR). DDCAR has a long half-life of 1-3 weeks and is the predominant circulating active moiety. Efficacy and safety in persons with acute schizophrenia were assessed in four similarly designed, short-term, randomized, placebo-controlled clinical trials in nonelderly adults, with three studies considered positive and yielding a number needed to treat vs placebo for response (change from baseline ≥30% in Positive and Negative Syndrome Scale total score) of ten for the approved dose range of cariprazine 1.5-6 mg/day. The most common adverse reactions were extrapyramidal symptoms (15% and 19% for 1.5-3 and 4.5-6 mg/day, respectively, vs 8% for placebo) and akathisia (9% and 12.5% for 1.5-3 and 4.5-6 mg/day, respectively, vs 4% for placebo). For the approved dose range, rates of discontinuation because of an adverse event were lower overall for patients receiving cariprazine vs placebo (9% vs 12%). Weight and metabolic profile appear favorable. Cariprazine does not increase prolactin levels or prolong the electrocardiographic QT interval. Cariprazine has also been found to be effective for the maintenance treatment of schizophrenia by delaying time to relapse when compared with placebo (HR 0.45). A 26-week randomized clinical trial evidenced superiority of cariprazine over risperidone for the treatment of predominantly negative symptoms in patients with schizophrenia. Cariprazine is also approved in the US for the acute treatment of manic or mixed episodes associated with bipolar I disorder in adults and is being studied for the treatment of bipolar I depression and major depressive disorder.

The activity of brain and liver cytochrome P450 2D (CYP2D) is differently affected by antidepressants in the chronic mild stress (CMS) model of depression in the rat

The effect of two second-generation antidepressants escitalopram and venlafaxine on the activity of brain and liver cytochrome P450 2D (CYP2D) involved in the metabolism of psychotropics and neurotransmitters was determined in the chronic mild stress (CMS) model of depression. Escitalopram or venlafaxine (10 mg/kg ip/day each) were administered to control and CMS rats for 5 weeks. The activity of CYP2D was studied by measurement of the rate of bufuralol 1'-hydroxylation in microsomes derived from the liver or different brain structures. The obtained results indicate that CMS and the studied antidepressants had different effects on the CYP2D activity depending on the location of the enzyme. In the brain, CMS produced an increase in the CYP2D activity in the hippocampus. Chronic escitalopram or venlafaxine had no effect on the CYP2D activity in the brain of nonstressed rats, however, the antidepressants increased the enzyme activity in the frontal cortex, hypothalamus and cerebellum of stressed animals. In the liver, CMS did not affect the CYP2D activity, while chronic escitalopram or venlafaxine significantly decreased the CYP2D activity and protein level in nonstressed and stressed rats. We conclude that: 1) CMS stimulates the CYP2D activity in the hippocampus and triggers the stimulatory effect of antidepressants on CYP2D in other brain structures; 2) the local brain metabolism of CYP2D substrates (neurosteroids, neurotransmitters, psychotropics) may be enhanced by CMS and/or antidepressants; 3) in contrast to the brain, the liver metabolism of CYP2D substrates may be slower during long-term treatment with escitalopram or venlafaxine.

Genes associated with anhedonia: a new analysis in a large clinical trial (GENDEP)

A key feature of major depressive disorder (MDD) is anhedonia, which is a predictor of response to antidepressant treatment. In order to shed light on its genetic underpinnings, we conducted a genome-wide association study (GWAS) followed by investigation of biological pathway enrichment using an anhedonia dimension for 759 patients with MDD in the GENDEP study. The GWAS identified 18 SNPs associated at genome-wide significance with the top one being an intronic SNP (rs9392549) in PRPF4B (pre-mRNA processing factor 4B) located on chromosome 6 (P = 2.07 × 10-9) while gene-set enrichment analysis returned one gene ontology term, axon cargo transport (GO: 0008088) with a nominally significant P value (1.15 × 10-5). Furthermore, our exploratory analysis yielded some interesting, albeit not statistically significant genetic correlation with Parkinson's Disease and nucleus accumbens gray matter. In addition, polygenic risk scores (PRSs) generated from our association analysis were found to be able to predict treatment efficacy of the antidepressants in this study. In conclusion, we found some markers significantly associated with anhedonia, and some suggestive findings of related pathways and biological functions, which could be further investigated in other studies.

The novel atypical antipsychotic cariprazine demonstrates dopamine D2 receptor-dependent partial agonist actions on rat mesencephalic dopamine neuronal activity

Aim

Cariprazine, a dopamine D₃‐preferring D₃/D₂ receptor partial agonist, is FDA approved for the treatment of schizophrenia and acute manic or mixed episodes of bipolar disorder. This study used in vivo electrophysiological techniques in anesthetized rats to determine cariprazine's effect on dopaminergic cell activity in the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc).

Methods

Extracellular recordings of individual dopaminergic neurons were performed after oral or intravenous administration of cariprazine, the D₃ receptor antagonist SB 277011A, the D₂ receptor antagonist L741,626, and/or the D₃ receptor agonist PD 128,907.

Results

Acute oral treatment with cariprazine significantly increased and chronic cariprazine significantly decreased the number of spontaneously firing dopaminergic neurons in the VTA, but not in the SNc. Intravenous administration of cariprazine partially but significantly inhibited dopaminergic neuronal firing in both regions, which was prevented by L741,626 but not SB 277011A. In both VTA and SNc, cariprazine, SB 277011A, and L741,626 significantly antagonized the suppression of dopamine cell firing elicited by PD 128,907.

Conclusions

Cariprazine significantly modulates the number of spontaneously active VTA dopamine neurons and moderately suppresses midbrain dopamine neuronal activity. The contribution of dopamine D₂ receptors to cariprazine's in vivo effects is prevalent and that of D₃ receptors is less apparent.

The preclinical discovery and development of cariprazine for the treatment of schizophrenia

INTRODUCTION

Cariprazine is approved in the United States and Europe for the treatment of manic or mixed episodes associated with bipolar I disorder and for the treatment of schizophrenia in adult patients. It is typically administered orally once a day (a dose range 1.5 - 6 mg/day), does require titration, and may be given with or without food. It has a half-life of 2 - 4 days with an active metabolite that has a terminal half-life of 2 - 3 weeks. Areas covered: This review article focuses on the preclinical discovery of cariprazine providing details regarding its pharmacological, behavioral, and neurochemical mechanisms and its contribution to clinical therapeutic benefits. This article is based on the available literature with respect to the preclinical and clinical findings and product labels of cariprazine. Expert opinion: Cariprazine shows highest affinity toward D₃ receptors, followed by D₂, 5-HT_2B, and 5-HT_1A receptors. It also shows moderate affinity toward σ₁, 5-HT_2A, and histamine H₁ receptors. Long-term administration of cariprazine altered the abundance of dopamine, serotonin, and glutamate receptor subtypes in different brain regions. All these mechanisms of cariprazine may contribute toward its unique preclinical profile and its clinically observed benefits in the treatment of schizophrenia, bipolar mania, and possibly other psychiatric disorders.

Aripiprazole relieves motivational anhedonia in rats

BACKGROUND

Anhedonia is considered a relevant feature in depression and psychosis, characterized by poor treatment outcome, and associated with deficits in mesolimbic dopaminergic responsiveness. Clinical studies suggest the potential utility of aripiprazole as adjunctive therapy for resistant depression. Since aripiprazole can stabilize the dopaminergic system, in search of tailored therapeutic strategies for reward dysfunctions, we investigated whether the drug restored motivation toward positive stimuli in a rat model.

METHODS

Anhedonia is modeled in non food-deprived 9-week old male Sprague-Dawley rats by exposing them to a chronic unavoidable stress protocol, consisting in repeated exposure to tail-shock or restrain, which disrupts the motivation to acquire a reward-directed behavior and the competence to escape aversive stimuli. We evaluated whether long-term aripiprazole administration (1mg/kg/day, i.p.) restored in chronically stressed rats, a) the disrupted dopaminergic response to sucrose consumption measuring DARPP-32 phosphorylation levels in the nucleus accumbens shell by immunoblotting; b) the motivation to operate in a sucrose self-administration protocol.

RESULTS

Long-term aripiprazole administration restored DARPP-32 phosphorylation changes in response to sucrose and reinstated the motivational drive to acquire the reward in the progressive ratio task. However, it did not restore reactivity to aversive stimuli.

LIMITATIONS

The results obtained in our model may not fully translate to the clinic, as anhedonia is a complex construct in patients, where motivational aspects represent a central but not unique feature.

CONCLUSIONS

This study demonstrates that aripiprazole relieved motivational anhedonia in a stress-induced model and warrants further studies to ascertain whether this activity is clinically relevant for antipsychotic or adjunctive antidepressant treatments.

Spotlight on once-monthly long-acting injectable aripiprazole and its potential as maintenance treatment for bipolar I disorder in adult patients

The lack of long-term medication adherence is a challenge in the treatment of bipolar disorder, particularly during the maintenance phase when symptoms are less prominent. The rate of nonadherence is ~20%-60% depending on how strict a definition is used. Nonadherence worsens the course of bipolar disorder and can add hundreds of thousands of dollars to the lifetime cost of treating the illness. Long-acting injectable (LAI) medication is an attractive alternative to daily dosing of oral medication, especially among patients who are ambivalent about treatment. The purpose of this paper is to review the evidence for the safety and efficacy of LAI aripiprazole, which was recently approved for the treatment of bipolar disorder. The approval was based on a single double-blind, placebo-controlled, multisite trial that recruited participants from 103 sites in 7 countries. A total of 731 participants with bipolar disorder were enrolled in the study. Out of that total, 266 were successfully stabilized on LAI aripiprazole and entered the randomization phase. Treatment-emergent adverse events were, for the most part, mild to moderate. Akathisia was the most common adverse event, which, combined with restlessness, was experienced by 23% of the sample. At the end of the 52-week study period, nearly twice as many LAI-treated participants remained stable compared to those treated with placebo. Stability during the maintenance phase is arguably the most important goal of treatment. It is during this period of relative freedom from symptoms that patients are able to build a meaningful and satisfying life. The availability of a new treatment agent, particularly one that has the potential to enhance long-term adherence, is a welcome development.

Long-term effects of aripiprazole exposure on monoaminergic and glutamatergic receptor subtypes: comparison with cariprazine

OBJECTIVE

This study examined the chronic effects of aripiprazole and cariprazine on serotonin (5-HT1A and 5-HT2A) and glutamate (NMDA and AMPA) receptor subtypes. In addition, the effects of aripiprazole on D2 and D3 receptors were tested and compared with previously reported cariprazine data.

METHODS

Rats received vehicle, aripiprazole (2, 5, or 15 mg/kg), or cariprazine (0.06, 0.2, or 0.6 mg/kg) for 28 days. Receptor levels were quantified using autoradiographic assays on brain sections from the medial prefrontal cortex (MPC), dorsolateral frontal cortex (DFC), nucleus accumbens (NAc), caudate-putamen medial (CPu-M), caudate-putamen lateral (CPu-L), hippocampal CA1 (HIPP-CA1) and CA3 (HIPP-CA3) regions, and the entorhinal cortex (EC).

RESULTS

Similar to previous findings with cariprazine, aripiprazole upregulated D2 receptor levels in various regions; D3 receptor changes were less than those reported with cariprazine. All aripiprazole doses and higher cariprazine doses increased 5-HT1A receptors in the MPC and DFC. Higher aripiprazole and all cariprazine doses increased 5-HT1A receptors in HIPP-CA1 and HIPP-CA3. Aripiprazole decreased 5-HT2A receptors in the MPC, DFC, HIPP-CA1, and HIPP-CA3 regions. Both compounds decreased NMDA receptors and increased AMPA receptors in select brain regions.

CONCLUSIONS

Long-term administration of aripiprazole and cariprazine had similar effects on 5-HT1A, NMDA, and AMPA receptors. However, cariprazine more profoundly increased D3 receptors while aripiprazole selectively reduced 5-HT2A receptors. These results suggest that the unique actions of cariprazine on dopamine D3 receptors, combined with its effects on serotonin and glutamate receptor subtypes, may confer the clinical benefits, safety, and tolerability of this novel compound in schizophrenia and bipolar mania.

Cariprazine Exhibits Anxiolytic and Dopamine D3 Receptor-Dependent Antidepressant Effects in the Chronic Stress Model

Background

Cariprazine, a D3-preferring dopamine D2/D3 receptor partial agonist, is a new antipsychotic drug recently approved in the United States for the treatment of schizophrenia and bipolar mania. We recently demonstrated that cariprazine also has significant antianhedonic-like effects in rats subjected to chronic stress; however, the exact mechanism of action for cariprazine's antidepressant-like properties is not known. Thus, in this study we examined whether the effects of cariprazine are mediated by dopamine D3 receptors.

Methods

Wild-type and D3-knockout mice were exposed to chronic unpredictable stress for up to 26 days, treated daily with vehicle, imipramine (20 mg/kg), aripiprazole (1 and 5 mg/kg), or cariprazine (0.03, 0.1, 0.2, and 0.4 mg/kg), and tested in behavioral assays measuring anhedonia and anxiety-like behaviors.

Results

Results showed that cariprazine significantly attenuated chronic unpredictable stress-induced anhedonic-like behavior in wild-type mice, demonstrating potent antidepressant-like effects comparable with aripiprazole and the tricyclic antidepressant imipramine. This antianhedonic-like effect of cariprazine was not observed in D3-knockout mice, suggesting that the cariprazine antidepressant-like activity is mediated by dopamine D3 receptors. Moreover, cariprazine significantly reduced drinking latency in the novelty-induced hypophagia test in wild-type mice, further confirming its antianhedonic-like effect and showing that it also has anxiolytic-like activity.

Conclusions

In combination with previous studies, these results suggest that cariprazine has a unique pharmacological profile and distinct dopamine D3 receptor-dependent mechanism of action that may be beneficial in the treatment of schizophrenia, bipolar disorder, and major depressive disorder.

Cariprazine for the Treatment of Bipolar Disorder

PURPOSE

To review the data regarding a new antipsychotic, cariprazine.

CONCLUSIONS

Cariprazine is a dopamine D3, D2 partial agonist, with greater affinity to D3. It has been examined for schizophrenia, bipolar mania, bipolar depression, and unipolar depression. It has demonstrated efficacy in schizophrenia and mania, and has recently been approved by the U.S. Food and Drug Administration. However, it has a more inconsistent effect in depression, both unipolar and bipolar. Adverse effects include extrapyramidal symptoms, akathisia, and gastrointestinal distress.

PRACTICE IMPLICATIONS

Cariprazine will be a promising addition in the treatment of patients with acute mania and schizophrenia.

Managing Negative Symptoms of Schizophrenia: How Far Have We Come?

The specific efficacy of antipsychotics on negative symptoms is questionable, suggesting an urgent need for specific treatments for negative symptoms. This review includes studies published since 2014 with a primary or secondary focus on treating negative symptoms in schizophrenia. Special emphasis is given to recently published meta-analyses. Topics include novel pharmacological approaches, including glutamatergic-based and nicotinic-acetylcholinergic treatments, treatments approved for other indications by the US FDA (or other regulatory bodies) (antipsychotics, antidepressants, and mood stabilizers), brain stimulation, and behavioral- and activity-based approaches, including physical exercise. Potential complications regarding the design of current negative symptom trials are discussed and include inconsistent placebo effects, lack of reliable biomarkers, negative symptom scale and inclusion criteria variability, attempts to distinguish between primary and secondary negative symptoms, lack of focus on early psychosis, and the potential iatrogenic bias of clinical trials.

Cariprazine versus risperidone monotherapy for treatment of predominant negative symptoms in patients with schizophrenia: a randomised, double-blind, controlled trial

BACKGROUND

Although predominant negative symptoms of schizophrenia can be severe enough to cause persistent impairment, effective treatment options are lacking. We aimed to assess the new generation antipsychotic cariprazine in adult patients with predominant negative symptoms.

METHODS

In this randomised, double-blind, phase 3b trial, we enrolled adults aged 18-65 years with long-term (>2 year), stable schizophrenia and predominant negative symptoms (>6 months) at 66 study centres (mainly hospitals and university clinics, with a small number of private practices) in 11 European countries. Patients were randomly assigned (1:1) by an interactive web response system to 26 weeks of monotherapy with fixed-dose oral cariprazine (3 mg, 4·5 mg [target dose], or 6 mg per day) or risperidone (3 mg, 4 mg [target dose], or 6 mg per day); previous medication was discontinued over 2 weeks. The primary outcome was change from baseline to week 26 or end of treatment on the Positive and Negative Syndrome Scale factor score for negative symptoms (PANSS-FSNS) analysed in a modified intention-to-treat population of patients who had follow-up assessments within 5 days after last receipt of study drugs with a mixed-effects model for repeated measures. Safety was assessed in all patients who received at least one dose of study drug. This study is registered with EudraCT, number 2012-005485-36.

FINDINGS

Between May 27, 2013, and Nov 17, 2014, 533 patients were screened and 461 (86%) patients were randomised to treatment (230 for cariprazine and 231 for risperidone); 460 were included in the safety population (one patient discontinued before study drug intake). 227 (99%) of 230 patients in the cariprazine group and 229 (99%) of 230 patients in the risperidone group were included in the modified intention-to-treat population (178 [77%] in each group completed 26 weeks of treatment). Mean daily doses were 4·2 mg (SD 0·6) for cariprazine and 3·8 mg (0·4) for risperidone. Treatment-emergent adverse events (eg, insomnia, akathisia, worsening of schizophrenia, headache, anxiety) were reported in 123 (54%) patients treated with cariprazine and 131 (57%) patients treated with risperidone. Use of cariprazine led to a greater least squares mean change in PANSS-FSNS from baseline to week 26 than did risperidone (-8·90 points for cariprazine vs -7·44 points for risperidone; least squares mean difference -1·46, 95% CI -2·39 to -0·53; p=0·0022; effect size 0·31). One patient in the risperidone group died of a cause regarded as unrelated to treatment.

INTERPRETATION

Our results support the efficacy of cariprazine in the treatment of predominant negative symptoms of schizophrenia.

FUNDING

Gedeon Richter Plc.

Dopaminergic mechanisms in memory consolidation and antidepressant reversal of a chronic mild stress-induced cognitive impairment`

Cognitive deficits in depression can be modelled using the novel object recognition (NOR) test, performance in which is impaired by chronic mild stress (CMS). We aimed to examine the involvement of mesocorticolimbic DA terminal regions, and to establish the substrate for CMS-induced impairment of NOR and its reversal by chronic antidepressant treatment. In experiments 1 and 2, we examined the effect of infusions into medial PFC, dorsal hippocampus (HPC), and nucleus accumbens (NAc) shell of D1 and D2 antagonists and D3 agonist, which were predicted to impair NOR with a short (1 h) delay, and of D1 and D2 agonists and D3 antagonist, which were predicted to facilitate NOR with a long (24 h) delay. Using optimal doses identified in experiment 2, in experiments 3 and 4, we examined effects on drug-stimulated NOR of CMS and chronic treatment with venlafaxine (VFX) or risperidone (RSP). We found a wide involvement of DA systems in memory for NOR: D1 receptors in PFC, HPC, and NAc; D3 receptors in PFC and HPC; and D2 receptors in PFC. CMS impaired D2- and D3-mediated effects in PFC and HPC; antidepressants rescued those effects in PFC but not HPC. The involvement of DA in NOR is multifaceted, but the effects of CMS and antidepressants are more discrete, involving D2 and D3 receptors in PFC specifically. While raising many difficult questions, these results suggest that the D2 and D3 receptors in the medial PFC may be an important substrate for cognitive deficits in depression and their remediation.

Update on schizophrenia and bipolar disorder: focus on cariprazine

Schizophrenia and bipolar disorder are severe psychiatric disorders that are frequently associated with persistent symptoms and significant dysfunction. While there are a multitude of psychopharmacologic agents are available for treatment of these illnesses, suboptimal response and significant adverse consequences limit their utility. Cariprazine is a new, novel antipsychotic medication with dopamine D2 and D3 partial agonist effects. Its safety and efficacy have been investigated in acute psychosis of schizophrenia, bipolar mania, bipolar depression, and unipolar depression. Efficacy has been demonstrated in schizophrenia and mania. It is unclear if cariprazine is effective in depression associated with unipolar or bipolar illness. Adverse consequences include extrapyramidal symptoms including akathisia, and various gastrointestinal symptoms. The US Food and Drug Administration (FDA) has recently approved cariprazine. This review will provide clinicians with basic information regarding the research program of cariprazine.

Cariprazine in the treatment of schizophrenia: a proof-of-concept trial

This 6-week, double-blind, placebo-controlled, proof-of-concept study evaluated the efficacy, safety, and tolerability of low-dose (1.5-4.5 mg/day) and high-dose (6-12 mg/day) cariprazine in patients with acute exacerbation of schizophrenia (NCT00404573). The primary efficacy measure was change in the Positive and Negative Syndrome Scale (PANSS) total score, analyzed using a last observation carried forward approach. Other efficacy measures included the Clinical Global Impression-Severity (secondary) and PANSS subscales (additional). There were no significant differences between the two doses of cariprazine and placebo in PANSS total score change or any other efficacy parameter after multiplicity adjustment. However, low-dose cariprazine versus placebo showed significantly greater reductions in PANSS total (P=0.033) and PANSS negative (P=0.027) scores without multiplicity adjustment. Common treatment-emergent adverse events (incidence≥5% and twice that in the placebo group in either cariprazine dose group) were akathisia, restlessness, tremor, back pain, and extrapyramidal disorder. In this study, the overall cariprazine treatment effect was not statistically significant, but patients treated with low-dose cariprazine showed significantly greater improvement in schizophrenia symptoms relative to placebo-treated patients. Cariprazine was generally well tolerated. Results of this study suggest that cariprazine may be effective in treating schizophrenia and future research is warranted.