RETRACTED: Identification of metabolites of brexpiprazole in human urine for use in monitoring patient compliance

An overview of the efficacy and safety of brexpiprazole for the treatment of schizophrenia in adolescents

INTRODUCTION

The onset of psychotic symptoms occurs prior to age 19 in 39% of the patients with schizophrenia. There are limited approved treatment options for adolescents with schizophrenia. Brexpiprazole was approved by the United States Food and Drug Administration (FDA) for treatment of schizophrenia in adolescents in 2022.

AREAS COVERED

Extrapolation of adult data to youth and use of pharmacologic modeling coupled with open long-term safety data were used by the FDA to approve brexpiprazole for adolescent schizophrenia. They were all reviewed herein.

EXPERT OPINION

D2 receptor partial agonist antipsychotic agents are preferred in the early phase of treatment of psychotic disorders. Approval of brexpiprazole in adolescent schizophrenia provides an additional option. Brexpiprazole was approved by the FDA on the basis of extrapolation of adult data without controlled trials in adolescents. This reduces placebo exposure in young people. Two previous agents (asenapine and ziprasidone) approved for adult schizophrenia failed to separate from placebo in adolescent schizophrenia studies; this partially undermines the process of extrapolation. For brexpiprazole, the paucity of data in adolescents relegates it to a second-line agent. More research on brexpiprazole is needed to delineate its relative role in the management of adolescent schizophrenia.

Dopamine partial agonists: a discrete class of antipsychotics

Worldwide, there are now three marketed dopamine D2 partial agonists: aripiprazole, brexpiprazole and cariprazine. These three drugs share a number of properties other than their action at D2 receptors. Pharmacologically, they are 5HT2 antagonists and D3 and 5HT1A partial agonists but with little or no alpha-adrenergic, anticholinergic or antihistaminic activity. They also share a long duration of action. Clinically, D2 partial agonists are effective antipsychotics and generally have useful antimanic and antidepressant activity. They are usually well tolerated, causing akathisia and insomnia only at the start of treatment, and are non-sedating. These drugs also share a very low risk of increased prolactin and of weight gain and accompanying metabolic effects. They may also have a relatively low risk of tardive dyskinesia. There is some evidence that they are preferred by patients to dopamine antagonists. Individual dopamineD2 partial agonists have much in common and as a group they differ importantly from dopamine D2 antagonists. Dopamine D2 partial agonists should be considered a distinct class of antipsychotics.Key pointsD2 partial agonists share many pharmacological and clinical propertiesD2 partial agonists differ in several important respects from D2 antagonistsD2 partial agonists should be considered a discrete class of antipsychotics.

Current Status of Therapeutic Drug Monitoring in Mental Health Treatment: A Review

Therapeutic drug monitoring (TDM) receives growing interest in different psychiatric clinical settings (emergency, inpatient, and outpatient services). Despite its usefulness, TDM remains underemployed in mental health. This is partly due to the need for evidence about the relationship between drug serum concentration and efficacy and tolerability, both in the general population and even more in subpopulations with atypical pharmacokinetics. This work aims at reviewing the scientific literature published after 2017, when the most recent guidelines about the use of TDM in mental health were written. We found 164 pertinent records that we included in the review. Some promising studies highlighted the possibility of correlating early drug serum concentration and clinical efficacy and safety, especially for antipsychotics, potentially enabling clinicians to make decisions on early laboratory findings and not proceeding by trial and error. About populations with pharmacokinetic peculiarities, the latest studies confirmed very common alterations in drug blood levels in pregnant women, generally with a progressive decrease over pregnancy and a very relevant dose-adjusted concentration increase in the elderly. For adolescents also, several drugs result in having different dose-related concentration values compared to adults. These findings stress the recommendation to use TDM in these populations to ensure a safe and effective treatment. Moreover, the integration of TDM with pharmacogenetic analyses may allow clinicians to adopt precise treatments, addressing therapy on an individual pharmacometabolic basis. Mini-invasive TDM procedures that may be easily performed at home or in a point-of-care are very promising and may represent a turning point toward an extensive real-world TDM application. Although the highlighted recent evidence, research efforts have to be carried on: further studies, especially prospective and fixed-dose, are needed to replicate present findings and provide clearer knowledge on relationships between dose, serum concentration, and efficacy/safety.

Weekly Supervised Administration of Oral Antipsychotics: An Alternative to Long-Acting Injections?

Maintenance of response in schizophrenia is largely dependent on compliance with antipsychotic treatment. When people with schizophrenia are responsible for their own treatment, partial or non-adherence is common and usually results in relapse. Assured compliance with antipsychotic treatment is possible when long-acting injectable antipsychotics are given by healthcare staff, but some patients may not consent to treatment for a variety of reasons. An alternative to long-acting injections is the use of supervised oral administration of long-acting antipsychotics. This method assures compliance with prescribed regimens without the need for injections. To be suitable for once-weekly administration as an oral formulation, an antipsychotic needs to have a sufficiently long duration of action and to be well tolerated in high doses. There is evidence that weekly oral administration of either pimozide or penfluridol is effective and well tolerated in the treatment of schizophrenia. Other drugs potentially suitable for once-weekly oral administration include aripiprazole, brexpiprazole and cariprazine.

1-(Benzo[b]thiophen-4-yl)piperazine Ring Induced Bioactivation of Brexpiprazole in Liver Microsomes: Identification and Characterization of Reactive Conjugates Using Ultra-High-Performance Liquid Chromatography/Quadrupole Time-of-Flight Mass Spectrometry

BACKGROUND AND OBJECTIVES

Brexpiprazole is an atypical antipsychotic approved for the treatment of schizophrenia and major depressive disorders in adults. The structure of brexpiprazole contains well-known structural alerts like a thiophene ring, piperazine ring and quinolinone motifs. Additionally, the literature reveals that its structural analog, aripiprazole, could generate reactive intermediates. However, the bioactivation potential of brexpiprazole is yet unknown. Therefore, this study was planned to identify and characterize reactive adducts of brexpiprazole and its metabolites.

METHODS

Based on the reactivity, the potential atomic sites for a reactive intermediate generation were predicted by a xenosite web predictor tool for glutathione, cyanide, protein and DNA. To study the metabolic activation of brexpiprazole, the drug was individually incubated for 2 h at 37 °C with pooled male rat liver microsomes and human liver microsomes in microcentrifuge tubes fortified with glutathione/N-acetyl cysteine. Nicotinamide adenine dinucleotide phosphate reduced tetrasodium salt was used as a co-factor.

RESULTS

A total of six glutathione and N-acetyl cysteine conjugates of brexpiprazole metabolites were identified and characterized using ultra-high-performance liquid chromatography/quadrupole time-of-flight tandem mass spectrometry. Reactive metabolite 1 (RM1), RM3, RM4 and RM6 reactive conjugates were formed due to reactive quinone-imine or quinone intermediates, while RM2 and RM5 reactive adducts were generated because of a thiophene-S-oxide intermediate.

CONCLUSION

Brexpirazole is bioactivated due to the presence of a 1-(benzo[b]thiophen-4-yl)piperazine ring in its structure. In contrast to aripiprazole, the quinolinone motif was found latent towards bioactivation in brexpiprazole.

Is there enough evidence to classify cycloalkyl amine substituents as structural alerts?

Basic amine substituents provide several pharmacokinetic benefits relative to acidic and neutral functional groups, and have been extensively utilized as substituents of choice in drug design. On occasions, basic amines have been associated with off-target pharmacology via interactions with aminergic G-protein coupled receptors, ion-channels, kinases, etc. Structural features associated with the promiscuous nature of basic amines have been well-studied, and can be mitigated in a preclinical drug discovery environment. In addition to the undesirable secondary pharmacology, α-carbon oxidation of certain secondary or tertiary cycloalkyl amines can generate electrophilic iminium and aldehyde metabolites, potentially capable of covalent adduction to proteins or DNA. Consequently, cycloalkyl amines have been viewed as structural alerts (SAs), analogous to functional groups such as anilines, furans, thiophenes, etc., which are oxidized to reactive metabolites that generate immunogenic haptens by covalently binding to host proteins. Detailed survey of the literature, however, suggests that cases where preclinical or clinical toxicity has been explicitly linked to the metabolic activation of a cycloalkyl amine group are extremely rare. Moreover, there is a distinct possibility for the formation of electrophilic iminium/amino-aldehyde metabolites with numerous cycloalkyl amine-containing marketed drugs, since stable ring cleavage products have been characterized as metabolites in human mass balance studies. In the present work, a critical analysis of the evidence for and against the role of iminium ions/aldehydes as mediators of toxicity is discussed with a special emphasis on often time overlooked detoxication pathways of these reactive species to innocuous metabolites.

A Dilute and Shoot LC–MS/MS Method for Antipsychotics in Urine

Adherence to prescribed antipsychotics is an ongoing problem. Traditionally, estimates of adherence have been made from patient interviews, pill counting and blood testing. A number of methods for the analysis of antipsychotics in blood have been reported for both therapeutic drug monitoring and postmortem testing for toxicity. This report details a dilute and shoot method for the analysis of 19 different antipsychotics and metabolites. The method takes advantage of earlier reports demonstrating unique, prevalent urine metabolites for aripiprazole, brexpiprazole, haloperidol and lurasidone to enhance sensitivity for these analytes. With a fast analysis time and minimal sample preparation, this method can be used for quantitation of antipsychotics in urine. Finally, this method has been used to test samples for over a year with the results summarized in this report. While further improvements are certainly possible, this method is selective and sensitive for this group of important compounds.

In silico, in vitro and in vivo metabolite identification of brexpiprazole using ultra-high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry

RATIONALE

Brexpiprazole is a novel serotonin-dopamine activity modulator approved by the USFDA in July 2015 for the treatment of schizophrenia and as an adjunctive therapy with other antidepressants for major depressive disorder in adults. However, limited numbers of metabolites are reported in the literature for brexpiprazole. Our prime intent behind this study is to revisit metabolite profiling of brexpiprazole and to identify and characterize all possible in vitro and in vivo metabolites.

METHODS

Firstly, the site of metabolism for brexpiprazole was predicted by a Xenosite web predictor model. Secondly, in vitro metabolite profiling was performed by incubating the drug individually with rat liver microsomes, human liver microsomes and rat S9 fraction at 37°C for 1 h in incubator shaker. Finally, for in vivo metabolite identification, a 50 mg kg^-1 dose of brexpiprazole was administered to male Sprague-Dawley rats and the presence of various metabolites was confirmed in rat plasma, urine and feces.

RESULTS

The predicted atomic site of metabolism was obtained as a color gradient by the Xenosite web predictor tool and, from this study, probable metabolites were listed. In total, 14 phase I and 2 phase II metabolites were identified and characterized in the in vitro and in vivo matrices using ultra-high-performance liquid chromatography/quadrupole time-of-flight tandem mass spectrometry (UHPLC/QTOF-MS/MS). The majority of metabolites were found in the sample incubated with human liver microsomes and in rat urine, while in the other matrices only a few metabolites were detected.

CONCLUSIONS

All the 16 metabolites were identified and characterized using UHPLC/QTOF-MS/MS. The study revealed that brexpiprazole is metabolized via hydroxylation, glucuronidation, S-oxidation, N-oxidation, dioxidation, oxidative deamination, N-dealkylation, etc.