Partial agonists of dopamine receptors: mechanisms and clinical effects of aripiprazole, brexpiprazole and cariprazine

Safety assessment of Brexpiprazole: Real-world adverse event analysis from the FAERS database

OBJECTIVE

This study aims to analysis adverse drug events (ADE) related to Brexpiprazole from the third quarter of 2015 to the first quarter of 2023 from FAERS database.

METHODS

The ADE data related to Brexpiprazole from 2015 Q3 to 2023 Q1 were collected. After standardizing the data, a variety of signal quantification techniques, including ROR, PRR, BCPNN, and MGPS were used for analysis.

RESULTS

Among the 8559 ADE reports with Brexpiprazole as the primary suspected drug, 178 preferred terms (PT) of adverse reactions spanning 27 different system organ classes (SOC) were identified. Specifically, Metabolism and nutrition disorders and Reproductive system and breast disorders were unique adverse reactions to Brexpiprazole, with the latter not mentioned in the official drug label. Moreover, uncommon but significantly strong ADE signals, such as Egocentrism, Pharmacophobia, and Compulsions were observed. Notably, Tardive dyskinesia (n = 317, ROR 103.87, PRR 102.21, IC 6.21, EBGM 96.17) and Extrapyramidal disorder (n = 104, ROR 31.17, PRR 31.00, IC 4.57, EBGM 30.44) exhibited relatively high occurrence rates and signal strengths. Additionally, Lactation disorder (n = 6, ROR 48.09, PRR 48.07, IC 2.63, EBGM 46.71) and Breast discharge (n = 10, ROR 23.18, PRR 23.17, IC 2.94, EBGM 22.86) were observed, both presenting strong ADE signals.

CONCLUSION

Brexpiprazole poses risks of various adverse reactions while providing therapeutic effects. In clinical applications, practitioners should closely monitor occurrences of Psychiatric disorders, Metabolism and nutrition disorders, Reproductive system and breast disorders, and other events.

Volumetric absorptive microsampling for the therapeutic drug monitoring of psychiatric patients treated with cariprazine

Psychiatric disorders are usually treated with antipsychotic agents belonging to different pharmacological and chemical classes, the most recent ones collectively known as "third-generation antipsychotics", such as cariprazine, approved in 2015 for the treatment of patients affected by schizophrenia. For these patients, a frequent therapeutic drug monitoring (TDM) becomes essential to assess compliance and to optimise and personalise their therapy, also due to cariprazine interindividual variability and narrow therapeutic range. In this study, a bioanalytical method featuring miniaturised sampling and pretreatment was developed, based on volumetric absorptive microsampling (VAMS) for TDM of psychiatric patients under cariprazine treatment and compared to a reference method based on fluid plasma analysis. Minimally invasive whole blood VAMS was coupled to an original instrumental method based on ultra-high performance liquid chromatography hyphenated to mass spectrometry (UHPLC-MS). A feasible and streamlined, yet reliable VAMS pretreatment protocol was carefully optimised and the VAMS-UHPLC-MS methodology was validated with satisfactory results in terms of linearity (r2 > 0.9970 in the 1.5-100 ng/mL range), precision (%RSD < 11.7), extraction yield (> 90.0 %) and matrix effect (8.2 ≤ %RE ≤ 10.9). Finally, the microsampling approach coupled to UHPLC-MS was successfully applied to the TDM of psychiatric patients treated with cariprazine and compared with standard fluid plasma analysis, providing reliable quali-quantitative results, and proving to be readily applicable to the clinical practice in TDM programs as a useful alternative to cariprazine plasma analysis. This is the first report of a successful microsampling application, and in particular the first report of VAMS application, for the TDM of cariprazine.

Chemical Modulators for Targeting Autism Spectrum Disorders: From Bench to Clinic

Autism spectrum disorders (ASD) are neurodevelopmental disorders characterized by diverse behavioral symptoms such as repetitive behaviors, social deficits, anxiety, hyperactivity, and irritability. Despite their increasing incidence, the specific pathological mechanisms of ASD are still unknown, and the degree and types of symptoms that vary from patient to patient make it difficult to develop drugs that target the core symptoms of ASD. Although various atypical antipsychotics and antidepressants have been applied to regulate ASD symptoms, these drugs can only alleviate the symptoms and do not target the major causes. Therefore, development of novel drugs targeting factors directly related to the onset of ASD is required. Among the various factors related to the onset of ASD, several chemical modulators to treat ASD, focused on serotonin (5-hydroxytryptamine, 5-HT) and glutamate receptors, microbial metabolites, and inflammatory cytokines, are explored in this study. In particular, we focus on the chemical drugs that have improved various aspects of ASD symptoms in animal models and in clinical trials for various ages of patients with ASD.

Potential Mechanisms for Why Not All Antipsychotics Are Able to Occupy Dopamine D3 Receptors in the Brain in vivo

Dysfunctions of the dopaminergic system are believed to play a major role in the core symptoms of schizophrenia such as positive, negative, and cognitive symptoms. The first line of treatment of schizophrenia are antipsychotics, a class of medications that targets several neurotransmitter receptors in the brain, including dopaminergic, serotonergic, adrenergic and/or muscarinic receptors, depending on the given agent. Although the currently used antipsychotics display in vitro activity at several receptors, majority of them share the common property of having high/moderate in vitro affinity for dopamine D₂ receptors (D₂Rs) and D₃ receptors (D₃Rs). In terms of mode of action, these antipsychotics are either antagonist or partial agonist at the above-mentioned receptors. Although D₂Rs and D₃Rs possess high degree of homology in their molecular structure, have common signaling pathways and similar in vitro pharmacology, they have different in vivo pharmacology and therefore behavioral roles. The aim of this review, with summarizing preclinical and clinical evidence is to demonstrate that while currently used antipsychotics display substantial in vitro affinity for both D₃Rs and D₂Rs, only very few can significantly occupy D₃Rs in vivo. The relative importance of the level of endogenous extracellular dopamine in the brain and the degree of in vitro D₃Rs receptor affinity and selectivity as determinant factors for in vivo D₃Rs occupancy by antipsychotics, are also discussed.

Partial agonists of dopamine receptors: receptor theory and the dopamine hypothesis of psychosis

This article discusses dopamine partial agonism, which is the main mechanism of action of the psychiatric drugs aripiprazole, brexpiprazole and cariprazine. It outlines the principles of receptor theory and the structure of dopamine receptors; characterises agonists, antagonists and partial agonists; and summarises the dopamine hypothesis of psychosis and the role of dopamine and serotonin in depression.