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

Rhabdomyolysis during adjunctive treatment with cariprazine in a clozapine-resistant schizophrenia patient

We report the case of a 49-year-old male treatment-resistant schizophrenia patient, whose treatment with clozapine and sertraline was supplemented with cariprazine 1.5 mg/day while regularly presenting for electroconvulsive therapy. After 3 weeks of adjunctive treatment with cariprazine, blood tests revealed pronounced signs of rhabdomyolysis, including a creatine kinase serum level of 20 386 U/L and an AST serum level of 696 U/L. Clinically, the patient did not report somatic symptoms other than mild back pain. After discontinuation of cariprazine and normal saline infusion, the above-mentioned findings resolved rapidly. Although very rare, rhabdomyolysis can be a potentially dangerous side effect of cariprazine and clinicians should be aware of its possible occurrence.

Pharmacological fingerprint of antipsychotic drugs at the serotonin 5-HT2A receptor

The intricate involvement of the serotonin 5-HT2A receptor (5-HT2AR) both in schizophrenia and in the activity of antipsychotic drugs is widely acknowledged. The currently marketed antipsychotic drugs, although effective in managing the symptoms of schizophrenia to a certain extent, are not without their repertoire of serious side effects. There is a need for better therapeutics to treat schizophrenia for which understanding the mechanism of action of the current antipsychotic drugs is imperative. With bioluminescence resonance energy transfer (BRET) assays, we trace the signaling signature of six antipsychotic drugs belonging to three generations at the 5-HT2AR for the entire spectrum of signaling pathways activated by serotonin (5-HT). The antipsychotic drugs display previously unidentified pathway preference at the level of the individual Gα subunits and β-arrestins. In particular, risperidone, clozapine, olanzapine and haloperidol showed G protein-selective inverse agonist activity. In addition, G protein-selective partial agonism was found for aripiprazole and cariprazine. Pathway-specific apparent dissociation constants determined from functional analyses revealed distinct coupling-modulating capacities of the tested antipsychotics at the different 5-HT-activated pathways. Computational analyses of the pharmacological and structural fingerprints support a mechanistically based clustering that recapitulate the clinical classification (typical/first generation, atypical/second generation, third generation) of the antipsychotic drugs. The study provides a new framework to functionally classify antipsychotics that should represent a useful tool for the identification of better and safer neuropsychiatric drugs and allows formulating hypotheses on the links between specific signaling cascades and in the clinical outcomes of the existing drugs.

Brexpiprazole in patients with schizophrenia with or without substance use disorder: an observational study

Background

Partial dopamine D2 receptor agonists are used for psychotic symptoms in adults with schizophrenia spectrum disorders. Recently, interest surged for partial dopamine D2 receptor agonists in substance use disorders (SUDs). Since it is believed that SUDs decrease the efficacy of pharmacotherapy of underlying psychiatric disorders, we tested the efficacy of the partial D2 agonist brexpiprazole in patients with schizophrenia who were either comorbid with a SUD (SUD group) or not comorbid (non-SUD) to assess treatment response and the effect of brexpiprazole on substance craving in SUD.

Methods

We included patients with DSM-5/DSM-5-TR schizophrenia (using SCID-5-CV) aged 18-66 years with either comorbid SUD or non-SUD to treat with brexpiprazole 4 mg/day for 6 months during February-October 2022. Patients were assessed with the Clinical Global Impressions-Severity (CGI-S) scale, the 24-item Brief Psychiatric Rating Scale (BPRS), and the Positive And Negative Syndrome Scale (PANSS) at baseline, weekly for the first 2 months and monthly for the next four. Furthermore, we assessed substance craving in SUD with a visual analog scale for craving (VAScrav) at the same timepoints.

Results

The total sample was 86 (85 analysable) 18- to 64-year-old (mean 39.32 ± 14.09) patients with schizophrenia [51 men (59.3%) and 35 women (40.7%)], of whom 48 SUD (55.8%) (37 men and 11 women) and 38 non-SUD (44.2%) (14 men and 24 women). No serious or persistent adverse events developed over the study period, but one patient dropped out for subjective akathisia. Results indicated the main effects of time with improvements over the course of the study for CGI-S, BPRS, and PANSS in both SUD and non-SUD groups and the entire sample, and for VAScrav in SUD. Brexpiprazole was associated with similar significant improvements in both groups at the 6 month endpoint compared to baseline.

Conclusion

Treatment with brexpiprazole for 6 months improved psychotic symptoms in patients with schizophrenia, independently from whether they belonged to the SUD or the non-SUD group; hence, SUD comorbidity did not confer treatment resistance to brexpiprazole. Furthermore, in the SUD group, we observed reduced substance craving.

A network meta-analysis of multiple modalities for the treatment of complex proximal humeral fractures in older adults

OBJECTIVE

Four principal treatment modalities are applied to treat complex proximal humeral fractures in older adults: conservative treatment, open reduction internal fixation, hemiarthroplasty, and reverse shoulder arthroplasty. However, among these, the optimal treatment modality has yet to be determined. Therefore, a network meta-analysis was carried out to compare treatment modalities and assess their effectiveness.

METHODS

The databases PUBMED, EM-BASE, the Cochrane Central Register of Controlled Trials, Web of Science, and CNKI were searched for randomised controlled trials on complex proximal humeral fractures in older people, ranging from inception of each database to May 2023.

RESULTS

This meta-analysis included 14 randomised controlled trials, containing 791 patients aged over 60 years who were treated for complex proximal humeral fractures. Reverse shoulder arthroplasty and hemiarthroplasty yielded the highest Constant shoulder scores, whilst conservative treatment performed poorly. Hemiarthroplasty and open reduction internal fixation yielded the best performances on the visual analogue pain scale, whilst conservative treatment performed poorly. Reverse shoulder arthroplasty and open reduction internal fixation allowed for maximum forward flexion and outreach of range of motion, whilst hemiarthroplasty allowed for the least. Open reduction internal fixation and reverse shoulder arthroplasty allowed for maximum internal rotation of the range of motion, whilst conservative treatment allowed for the least. Hemiarthroplasty and conservative treatment allowed for maximum external rotation of the range of motion, whilst open reduction internal fixation allowed for the least.

CONCLUSION

Compared with open reduction internal fixation, reverse shoulder arthroplasty yields better Constant shoulder scores and allows for greater forward flexion and outreach of range of motion of the shoulder joint in complex proximal humerus fractures in older patients. Meanwhile, hemiarthroplasty yields the best visual analogue scale scores and allows for maximum external rotation of the range of motion. However, open reduction with internal fixation remains the preferred clinical treatment for complex proximal humeral fractures in older patients.

Antidepressant efficacy of cariprazine in bipolar disorder and the role of its pharmacodynamic properties: A hypothesis based on data

The treatment of bipolar depression is one of the most challenging needs in contemporary psychiatry. Currently, only quetiapine, olanzapine-fluoxetine combination, lurasidone, cariprazine, and recently lumateperone have been FDA-approved to treat this condition. The neurobiology of bipolar depression and the possible targets of bipolar antidepressant therapy remain elusive. The current study investigated whether the pharmacodynamic properties of cariprazine fit into a previously developed model which was the first to be derived based on the strict combination of clinical and preclinical data. The authors performed a systematic review of the literature to identify the pharmacodynamic properties of cariprazine. The original model suggests that a constellation of effects on different receptors is necessary and that serotonin reuptake inhibition does not appear to play a significant role in acute bipolar depression. On the contrary, norepinephrine activity seems to be necessary. Probably the early antidepressant effect can be achieved through an agonistic activity at 5HT-1A and antagonism at alpha1 noradrenergic and 5-HT2A receptors, but the presence of a norepinephrine reuptake inhibition appears essential to sustain it. Overall, the properties of cariprazine fit well the proposed model and add to its validity. A point that needs further clarification is norepinephrine reuptake inhibition which is not yet fully studied for cariprazine.

Seventy Years of Antipsychotic Development: A Critical Review

Since the mid-1950s discovery of the first effective antipsychotic medications (APM), we have only been able to improve the tolerability but not the overall efficacy of currently available APMs, as reflected by effectiveness trials in Europe and the United States. This inability to develop more effective APMs is attributable to multiple factors, including failure to create and use assessment tools to assess core symptom domains in schizophrenia, move beyond the dopaminergic hypothesis and to develop "me too" drugs, imposing ill-defined research domain criteria, and lacking federal funding for clinical trials. The classification of APMs is also confusing, including second-generation, partial agonists, and multimodal APMs in the same class of APMs, despite significant differences in their mechanisms of action. Other factors stagnating drug development include inadequate sample sizes to address heterogeneity, lack of statistical measures correlating with clinical significance, using the atheoretical basis of psychiatric diagnoses, failure to control placebo response, and high cost of newer and perhaps more tolerable APMs. Furthermore, there has been a failure to develop early predictors of antipsychotic response and various tools to optimize an APM response. Finally, some mental health providers are also responsible for the suboptimal use of APMs, by using excessive maintenance doses, often with irrational polypharmacy, further compromising effectiveness and medication adherence. However, some bright spots in antipsychotic development include improved tolerability of APMs and long-acting injectables to address the high prevalence of medication nonadherence. This review critically reviews 70 years of antipsychotic development, the reasons behind the failure to develop more effective APMs, and suggestions for future direction.

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.

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.

Cariprazine Add-on in Inadequate Clozapine Response: A Report on Two Cases

Cariprazine is a novel antipsychotic drug that exerts partial agonism of dopamine D₂/D₃ receptors with preferential binding to the D₃ receptor, antagonism of 5HT_2B receptors, and partial agonism of 5HT_1A. Currently, cariprazine has shown clinical efficacy in patients with schizophrenia and with bipolar disorder, as well as adjunctive treatment in patients with Major Depressive Disorder (MDD) and drug-resistant MDD. In the present case series, we report on two patients with treatment-resistant schizophrenia and partial response to clozapine who benefit from combination with cariprazine. The effects of cariprazine combination were remarkable also concerning the adverse metabolic effects of clozapine.

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.

Synthesis and Biological Evaluation of Five-Atom-Linker-Based Arylpiperazine Derivatives with an Atypical Antipsychotic Profile

Herein we describe a focused set of new arylpiperazine derivatives as potential broad-spectrum antipsychotics. The general structure contains a quinolinone-like moiety, an arylpiperazine moiety, and a five-atom linker. Among them, 7-(5-(4-(benzo[d]isothiazol-4-yl)piperazin-1-yl)pentyl)quinolin-2(1H)-one (S6) shows a promising preclinical profile. Compound S6, characterized by partial D₂ R agonism, 5-HT_1A R agonism, 5-HT_2A R antagonism, and blockade of SERT activities, was found to decrease psychosis- and depressive-like symptoms in rodents. The polypharmacological profile of S6 could provide opportunities for the treatment of various other central nervous system disorders such as anxiety, depression, and psychoses associated with dementia. Furthermore, S6 demonstrated acceptable safety, toxicology, and pharmacokinetic profiles, and has been selected as a preclinical candidate for further evaluation in schizophrenia.

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.