Clinical and theoretical implications of 5-HT2 and D2 receptor occupancy of clozapine, risperidone, and olanzapine in schizophrenia

Direct effects of antipsychotics on potassium channels

Schizophrenia (SCZ) and bipolar disorder (BD) and are severe psychiatric conditions that contribute to disability and increased healthcare costs globally. Although first-, second-, and third-generation antipsychotics are available for treating BD and SCZ, most have various side effects unrelated to their unique functions. Many antipsychotics affect K+ channels (Kv, KCa, Kir, K2P, and other channels), which change the functions of various organs. This review summarizes the biological actions of antipsychotics, including off-target side effects involving K+ channels.

Clinical Correlates of Antipsychotic Plasma Levels with Long-Acting Paliperidone: Corrélats cliniques des concentrations plasmiques de palipéridone à libération prolongée

OBJECTIVES

The majority of patients with schizophrenia experience dramatic improvement in psychotic symptoms when treated with antipsychotic medication. Maintenance treatment can prevent relapses but problems with medication adherence limit effectiveness. Long-acting injectable antipsychotics (LAIs) provide an opportunity to establish adherence but challenges remain in ensuring that the dose selected is therapeutic. Therapeutic drug monitoring has not been established as valuable for LAIs in the maintenance treatment of schizophrenia. This exploratory study was undertaken to describe plasma paliperidone levels in outpatients treated with the LAI paliperidone palmitate and to determine whether paliperidone levels are associated with subjective experience on medication and side effects.

METHODS

Twenty-one outpatients with schizophrenia receiving treatment with LAI paliperidone consented to participation in this study. Blood samples were obtained for measurement of paliperidone and prolactin levels at the first visit. A second paliperidone level was obtained at the time of the next injection for 18 of the participants. Clinical rating scales were administered at the first visit to assess illness severity, attitudes regarding medication, subjective well-being and side effects.

RESULTS

Paliperidone levels were highly correlated at the two time points (ρ = .85; P < .001). Mean paliperidone level at the first visit was 34.9 ng/ml and ranged from 5.1 to 73.9 ng/ml. Higher paliperidone levels were correlated with higher prolactin levels (ρ = 0.59, P < .01) and lower sexual desire (ρ = -.58, P < .01).

CONCLUSIONS

We demonstrated that paliperidone levels can be measured reliably in patients receiving LAI paliperidone. Higher plasma levels were associated with higher prolactin levels and reduced sexual desire but not with measures of subjective experience on medications or other side effects. Measurement of paliperidone levels in patients treated with paliperidone palmitate may have the potential to minimize the dose of medication prescribed and, in turn, the severity of sexual side effects.

Optimisation of pharmacotherapy in psychiatry through therapeutic drug monitoring, molecular brain imaging and pharmacogenetic tests: Focus on antipsychotics

BACKGROUND

For psychotic disorders (i.e. schizophrenia), pharmacotherapy plays a key role in controlling acute and long-term symptoms. To find the optimal individual dose and dosage strategy, specialised tools are used. Three tools have been proven useful to personalise drug treatments: therapeutic drug monitoring (TDM) of drug levels, pharmacogenetic testing (PG), and molecular neuroimaging.

METHODS

In these Guidelines, we provide an in-depth review of pharmacokinetics, pharmacodynamics, and pharmacogenetics for 45 antipsychotics. Over 30 international experts in psychiatry selected studies that have measured drug concentrations in the blood (TDM), gene polymorphisms of enzymes involved in drug metabolism, or receptor/transporter occupancies in the brain (positron emission tomography (PET)).

RESULTS

Study results strongly support the use of TDM and the cytochrome P450 (CYP) genotyping and/or phenotyping to guide drug therapies. Evidence-based target ranges are available for titrating drug doses that are often supported by PET findings.

CONCLUSION

All three tools discussed in these Guidelines are essential for drug treatment. TDM goes well beyond typical indications such as unclear compliance and polypharmacy. Despite its enormous potential to optimise treatment effects, minimise side effects and ultimately reduce the global burden of diseases, personalised drug treatment has not yet become the standard of care in psychiatry.

A Comprehensive Review of Schizophrenia and Antipsychotic Metabolism as a Predictor of Treatment Response

Some patients with schizophrenia fail to respond to standard antipsychotics and are considered treatment-resistant. In these cases, clozapine is the only antipsychotic with proven efficacy, but its use is complicated by severe adverse effects, complex monitoring requirements, and non-response. Variation within the CYP450 enzymes CYP1A2, CYP2D6, CYP3A4, and CYP2C19 has been linked to the differential metabolism of antipsychotics. Testing for CYP450 single nucleotide polymorphisms may be a useful predictor of treatment resistance and could inform pharmacogenetic recommendations to identify potential treatment non-responders. Nonetheless, it remains uncertain whether differential antipsychotic metabolism is directly related to treatment efficacy. This comprehensive narrative review endeavours to delve into the molecular and genetic basis of schizophrenia, and discuss the current treatments available. In particular, we aim to examine the aetiology of treatment resistance in schizophrenia through available literature and discuss current challenges within the field.

Revealing receptor-ligand interactions of atypical antipsychotic drugs and screening anti-schizophrenia ingredients in Magnolia officinalis based on 5-HTR2A-SNAP-Tag/CMC and DRD2-SNAP-Tag/CMC models

Schizophrenia is a serious mental illness with unknown etiology, and shows increasing incidence and high lifetime prevalence rate. The main receptors related to the disease are DRD2 and 5-HTR2A. Thus, a comprehensive understanding of the interaction mode between antipsychotic drugs with relevant receptors is very important for developing more effective drugs. 5-HTR2A-SNAP-Tag/CMC and DRD2-SNAP-Tag/CMC models constructed in this work provided a new method for studying the interaction between atypical antipsychotics and the two receptors. The results of comparative experiments showed that the new models not only met the high selectivity and specificity of the screening requirements but were also more stable and long-lasting than the traditional CMC model. Binding assays showed that the effects of three atypical antipsychotics (including clozapine, olanzapine, and quetiapine) on 5-HTR2A were stronger than their effects on DRD2. Additionally, two potentially active components, magnolol and honokiol, were screened in Magnolia officinalis methanol extract using the 5-HTR2A-SNAP-Tag/CMCHPLC-MS system. Nonlinear chromatographic analysis and molecular docking were conducted to study the interactions between screened compounds and the two receptors. The binding constants (KA) of magnolol and honokiol with 5-HTR2A were 17,854 ± 1,117 M-1 and 38,858 ± 4,964 M-1, respectively, and KA values with DRD2 were 4,872 ± 1,618 M-1 and 20,692 ± 10,267 M-1, respectively. We concluded that the established models are reliable for studying receptor-ligand interactions and screening antagonists of schizophrenia.

Update Lessons from Positron Emission Tomography Imaging Part I: A Systematic Critical Review on Therapeutic Plasma Concentrations of Antipsychotics

BACKGROUND

Positron emission tomography (PET) and single photon emission tomography (SPECT) of molecular drug targets (neuroreceptors and transporters) provide essential information for therapeutic drug monitoring-guided antipsychotic drug therapy. The optimal therapeutic windows for D 2 antagonists and partial agonists, as well as their proposed target ranges, are discussed based on an up-to-date literature search.

METHODS

This part I of II presents an overview of molecular neuroimaging studies in humans and primates involving the target engagement of amisulpride, haloperidol, clozapine, aripiprazole, olanzapine, quetiapine, risperidone, cariprazine, and ziprasidone. The systemic review particularly focused on dopamine D 2 -like and 5-HT 2A receptors. Target concentration ranges were estimated based on receptor occupancy ranges that relate to clinical effects or side effects (ie, extrapyramidal side effects). In addition, findings for other relevant receptor systems were included to further enrich the discussion.

RESULTS

The reported reference ranges for aripiprazole and clozapine align closely with findings from PET studies. Conversely, for haloperidol, risperidone, and olanzapine, the PET studies indicate that a lowering of the previously published upper limits would be necessary to decrease the risk of extrapyramidal side effect.

CONCLUSIONS

Molecular neuroimaging studies serve as a strong tool for defining target ranges for antipsychotic drug treatment and directing therapeutic drug monitoring.

Extrapyramidal Side Effects with Chronic Atypical Antipsychotic Can Be Predicted by Labeling Pattern of FosB and phosphoThr34-DARPP-32 in Nucleus Accumbens

Extrapyramidal side effects (EPS) can be induced by neuroleptics that regulate the expression of transcription factor FosB and dopaminergic mediator DARPP-32 in the striatum. However, the long-term neurobiological changes in striatal projection neurons resulting from a cumulative dosage of typical and atypical antipsychotics are poorly understood. The present study aimed to determine the differential and long-lasting changes in FosB distribution and DARPP-32 phosphorylation in the striatum and nucleus accumbens (NAc) associated with chronic antipsychotic-induced EPS. Male C57Bl/6J mice received daily injections of Olanzapine (Olz, 15 mg/kg), Clozapine (Clz, 20 mg/kg), or Haloperidol (Hal, 1 mg/kg), for a period of 11 weeks with a 4-day withdrawal period before the last dosage. Catalepsy for detection of EPS, along with open-field and rotarod tests, were assessed as behavioral correlates of motor responses. Additionally, FosB and phosphorylated-DARPP-32 immunohistochemistry were examined in striatal regions after treatment. All antipsychotics produced catalepsy and reduced open-field exploration, such as impaired rota-rod performance after Olz and Hal. The washout period was critical for Clz-induced side effects reduction. Both Olz and Clz increased FosB in NAc Shell-region, and phosphoThr34-DARPP-32 in NAc. Only Clz reduced phosphoThr75-DARPP-32 in the dorsal striatum and showed FosB/phosphoThr34-Darpp-32-ir in the NAc Core region. This study provides evidence that atypical antipsychotics such as Olz and Clz also give rise to EPS effects frequently associated with a cumulative dosage of typical neuroleptics such as Hal. Nevertheless, FosB/phosphoThr34-Darpp-32-ir in the NAc Core region is associated with hypokinetic movements inhibition.

Olanzapine treatment effectively relieves breakthrough chemotherapy-induced nausea and vomiting: a real-world experience

BACKGROUND

Olanzapine treatment prevents chemotherapy-induced nausea and vomiting (CINV) in patients receiving highly emetogenic chemotherapy (HEC). However, its role in the secondary prevention of breakthrough CINV in real-world cancer care should be further evaluated.

METHOD

We conducted a retrospective study on patients receiving olanzapine to prevent breakthrough CINV refractory to standard antiemetic therapy. The major outcome was improvement in CINV, defined as any downgrade in CINV symptoms, according to the Common Terminology Criteria for Adverse Events. Comprete response was defined as no symptoms in CINV, i.e., Grade 0. These outcomes were compared in the HEC versus non-HEC groups and the standard- (5 or 10 mg/day) versus low- (2.5 mg/day) dose groups. The other outcome measurement was adverse events (AEs).

RESULTS

We analyzed 127 patients, including 92 women, with a median age of 50 years (range: 19-89 years). Baseline CINV severity was grade 1, 2, and 3 in 18%, 69%, and 13% of the patients, respectively. After prophylaxis with olanzapine at doses of 2.5, 5, or 10 mg/day, improvement was observed in 105 (83%) patients, with a complete response in 42 patients (33%). The improvement and complete remission rates for the HEC (n = 96) and non-HEC (n = 31) groups were 86% and 71% (p = 0.048) versus 38% and 19% (p = 0.062), respectively. The rates for the standard- (n = 98) and low- (n = 29) dose groups were 86% and 82% (p = 0.568) versus 28% and 52% (p = 0.015), respectively. Thirty-four patients (27%) experienced olanzapine-related AEs, mainly somnolence (n = 28). Grade 3 or higher AEs were not observed.

CONCLUSION

Our study results support the clinical application of olanzapine for the secondary prevention of breakthrough CINV.

Antipsychotic drug efficacy correlates with the modulation of D1 rather than D2 receptor-expressing striatal projection neurons

Elevated dopamine transmission in psychosis is assumed to unbalance striatal output through D1- and D2-receptor-expressing spiny-projection neurons (SPNs). Antipsychotic drugs are thought to re-balance this output by blocking D2 receptors (D2Rs). In this study, we found that amphetamine-driven dopamine release unbalanced D1-SPN and D2-SPN Ca2+ activity in mice, but that antipsychotic efficacy was associated with the reversal of abnormal D1-SPN, rather than D2-SPN, dynamics, even for drugs that are D2R selective or lacking any dopamine receptor affinity. By contrast, a clinically ineffective drug normalized D2-SPN dynamics but exacerbated D1-SPN dynamics under hyperdopaminergic conditions. Consistent with antipsychotic effect, selective D1-SPN inhibition attenuated amphetamine-driven changes in locomotion, sensorimotor gating and hallucination-like perception. Notably, antipsychotic efficacy correlated with the selective inhibition of D1-SPNs only under hyperdopaminergic conditions-a dopamine-state-dependence exhibited by D1R partial agonism but not non-antipsychotic D1R antagonists. Our findings provide new insights into antipsychotic drug mechanism and reveal an important role for D1-SPN modulation.

Informing individualized multi-scale neural signatures of clozapine response in patients with treatment-refractory schizophrenia

Clozapine is currently the only antipsychotic with demonstrated efficacy in treatment-refractory schizophrenia (TRS). However, response to clozapine differs widely between TRS patients, and there are no available clinical or neural predictive indicators that could be used to increase or accelerate the use of clozapine in patients who stand to benefit. Furthermore, it remains unclear how the neuropharmacology of clozapine contributes to its therapeutic effects. Identifying the mechanisms underlying clozapine's therapeutic effects across domains of symptomatology could be crucial for development of new optimized therapies for TRS. Here, we present results from a prospective neuroimaging study that quantitatively related heterogeneous patterns of clinical clozapine response to neural functional connectivity at baseline. We show that we can reliably capture specific dimensions of clozapine clinical response by quantifying the full variation across item-level clinical scales, and that these dimensions can be mapped to neural features that are sensitive to clozapine-induced symptom change. Thus, these features may act as "failure modes" that can provide an early indication of treatment (non-)responsiveness. Lastly, we related the response-relevant neural maps to spatial expression profiles of genes coding for receptors implicated in clozapine's pharmacology, demonstrating that distinct dimensions of clozapine symptom-informed neural features may be associated with specific receptor targets. Collectively, this study informs prognostic neuro-behavioral measures for clozapine as a more optimal treatment for selected patients with TRS. We provide support for the identification of neuro-behavioral targets linked to pharmacological efficacy that can be further developed to inform optimal early treatment decisions in schizophrenia.

Inhibition of Microglial GSK3β Activity Is Common to Different Kinds of Antidepressants: A Proposal for an In Vitro Screen to Detect Novel Antidepressant Principles

Depression is a major public health concern. Unfortunately, the present antidepressants often are insufficiently effective, whilst the discovery of more effective antidepressants has been extremely sluggish. The objective of this review was to combine the literature on depression with the pharmacology of antidepressant compounds, in order to formulate a conceivable pathophysiological process, allowing proposals how to accelerate the discovery process. Risk factors for depression initiate an infection-like inflammation in the brain that involves activation microglial Toll-like receptors and glycogen synthase kinase-3β (GSK3β). GSK3β activity alters the balance between two competing transcription factors, the pro-inflammatory/pro-oxidative transcription factor NFκB and the neuroprotective, anti-inflammatory and anti-oxidative transcription factor NRF2. The antidepressant activity of tricyclic antidepressants is assumed to involve activation of GS-coupled microglial receptors, raising intracellular cAMP levels and activation of protein kinase A (PKA). PKA and similar kinases inhibit the enzyme activity of GSK3β. Experimental antidepressant principles, including cannabinoid receptor-2 activation, opioid μ receptor agonists, 5HT2 agonists, valproate, ketamine and electrical stimulation of the Vagus nerve, all activate microglial pathways that result in GSK3β-inhibition. An in vitro screen for NRF2-activation in microglial cells with TLR-activated GSK3β activity, might therefore lead to the detection of totally novel antidepressant principles with, hopefully, an improved therapeutic efficacy.

Pharmacological and nonpharmacological augmentation treatments for clozapine-resistant schizophrenia: A systematic review and network meta-analysis with normalized entropy assessment

OBJECTIVE

To integrate all evidence derived from randomized controlled trials (RCTs) of both pharmacological and nonpharmacological augmentation interventions for clozapine-resistant schizophrenia (CRS).

METHODS

Six major electronic databases were systematically searched for RCTs published until July 10, 2021. The primary outcome was change in overall symptoms, and the secondary outcomes were positive and negative symptoms and acceptability. We performed random-effects network meta-analysis. Normalized entropy was calculated to examine the uncertainty of treatment ranking.

RESULTS

We identified 35 RCTs (1472 patients with 23 active augmentation treatments) with a mean daily clozapine dose of 440.80 (91.27) mg for 1168.22 (710.28) days. Network meta-analysis of overall symptoms (reported as standardized mean difference; 95 % confidence interval) with consistent results indicated that mirtazapine (-4.41; -5.61, -3.21), electroconvulsive therapy (ECT) (-4.32; -5.43, -3.21), and memantine (-2.02; -3.14, -0.91) were ranked as the best three treatments. For positive symptoms, ECT (-5.18; -5.86, -4.49) was ranked the best with less uncertainty. For negative symptoms, memantine (-3.38; -4.50, -2.26), duloxetine (-3.27; -4.25, -2.29), and mirtazapine (-1.73; -2.71, -0.74) were ranked the best three treatments with less uncertainty. All antipsychotics, N-methyl d-aspartate receptor agonists, and antiepileptics were not associated with more efficacy than placebo. Compared to placebo, only amisulpride had statistically significant lower discontinuation rate (risk ratio: 0.21; 95 % CI: 0.05, 0.93).

CONCLUSION

Add-on mirtazapine, ECT, and memantine were the most efficacious augmentation options for CRS. Data on other important outcomes such as cognitive functioning or quality of life were rarely reported, making further large-scale, well-designed RCTs necessary. (PROSPERO number, CRD42021262197.).

The role of neurotransmitter systems in mediating deep brain stimulation effects in Parkinson’s disease

Deep brain stimulation (DBS) is among the most successful paradigms in both translational and reverse translational neuroscience. DBS has developed into a standard treatment for movement disorders such as Parkinson’s disease (PD) in recent decades, however, specific mechanisms behind DBS’s efficacy and side effects remain unrevealed. Several hypotheses have been proposed, including neuronal firing rate and pattern theories that emphasize the impact of DBS on local circuitry but detail distant electrophysiological readouts to a lesser extent. Furthermore, ample preclinical and clinical evidence indicates that DBS influences neurotransmitter dynamics in PD, particularly the effects of subthalamic nucleus (STN) DBS on striatal dopaminergic and glutamatergic systems; pallidum DBS on striatal dopaminergic and GABAergic systems; pedunculopontine nucleus DBS on cholinergic systems; and STN-DBS on locus coeruleus (LC) noradrenergic system. DBS has additionally been associated with mood-related side effects within brainstem serotoninergic systems in response to STN-DBS. Still, addressing the mechanisms of DBS on neurotransmitters’ dynamics is commonly overlooked due to its practical difficulties in monitoring real-time changes in remote areas. Given that electrical stimulation alters neurotransmitter release in local and remote regions, it eventually exhibits changes in specific neuronal functions. Consequently, such changes lead to further modulation, synthesis, and release of neurotransmitters. This narrative review discusses the main neurotransmitter dynamics in PD and their role in mediating DBS effects from preclinical and clinical data.

Second-generation antipsychotic olanzapine attenuates behavioral and prefrontal cortex synaptic plasticity deficits in a neurodevelopmental schizophrenia-related rat model

Second-generation antipsychotics are the drugs of choice for the treatment of neurodevelopmental-related mental diseases such as schizophrenia. Despite the effectiveness of these drugs to ameliorate some of the symptoms of schizophrenia, specifically the positive ones, the mechanisms beyond their antipsychotic effect are still poorly understood. Specifically, second-generation antipsychotics are reported to have anti-inflammatory, antioxidant and neuroplastic properties. Using the neonatal ventral hippocampus lesion (nVHL) in the rat, an accepted schizophrenia-related model, we evaluated the effect of the second-generation antipsychotic olanzapine (OLZ) in the behavioral, neuroplastic, and neuroinflammatory alterations exhibited in the nVHL animals. OLZ corrected the hyperlocomotion and impaired working memory of the nVHL animals but failed to enhance social disturbances of these animals. In the prefrontal cortex (PFC), OLZ restored the pyramidal cell structural plasticity in the nVHL rats, enhancing the dendritic arbor length, the spinogenesis and the proportion of mature spines. Moreover, OLZ attenuated astrogliosis as well as some pro-inflammatory, oxidative stress, and apoptosis-related molecules in the PFC. These findings reinforce the evidence of anti-inflammatory, antioxidant, and neurotrophic mechanisms of second-generation antipsychotics in the nVHL schizophrenia-related model, which allows for the possibility of developing more specific drugs for this disorder and thus avoiding the side effects of current schizophrenia treatments.

High-frequency stimulation of the subthalamic nucleus induces a sustained inhibition of serotonergic system via loss of cell phenotype

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has become a standard treatment for Parkinson's disease (PD). However, in a considerable number of patients debilitating psychiatric side-effects occur. Recent research has revealed that external stimuli can alter the neurotransmitters' homeostasis in neurons, which is known as "neurotransmitter respecification". Herein, we addressed if neurotransmitter respecification could be a mechanism by which DBS suppresses the serotonergic function in the dorsal raphe nucleus (DRN) leading to mood changes. We infused transgenic 5-HT-Cre (ePET-Cre) mice with AAV viruses to achieve targeted expression of eYFP and the genetically encoded calcium indicator GCaMP6s in the DRN prior to methyl-4phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment. Mice received bilateral DBS electrodes in the STN and an optic fiber in the DRN for calcium photometry. MPTP-treated mice demonstrated behavioral and histological PD phenotype, whereas all STN-DBS animals exhibited an increased immobility time in the forced swim test, reduced calcium activity, and loss of tryptophan hydroxylase-2 expression in the DRN. Given the prominent role of calcium transients in mediating neurotransmitter respecification, these results suggest a loss of serotonergic phenotype in the DRN following STN-DBS. These findings indicate that loss of serotonergic cell phenotype may underlie the unwanted depressive symptoms following STN-DBS.

Synthesis and In Vitro Evaluation of Novel Dopamine Receptor D2 3,4-dihydroquinolin-2(1H)-one Derivatives Related to Aripiprazole

In this pilot study, a series of new 3,4-dihydroquinolin-2(1H)-one derivatives as potential dopamine receptor D₂ (D₂R) modulators were synthesized and evaluated in vitro. The preliminary structure-activity relationship disclosed that compound 5e exhibited the highest D₂R affinity among the newly synthesized compounds. In addition, 5e showed a very low cytotoxic profile and a high probability to cross the blood-brain barrier, which is important considering the observed affinity. However, molecular modelling simulation revealed completely different binding mode of 5e compared to USC-D301, which might be the culprit of the reduced affinity of 5e toward D₂R in comparison with USC-D301.

Interaction of clozapine with metformin in a schizophrenia rat model

The low efficacy of antipsychotic drugs (e.g., clozapine) for negative symptoms and cognitive impairment has led to the introduction of adjuvant therapies. Because previous data suggest the procognitive potential of the antidiabetic drug metformin, this study aimed to assess the effects of chronic clozapine and metformin oral administration (alone and in combination) on locomotor and exploratory activities and cognitive function in a reward-based test in control and a schizophrenia-like animal model (Wisket rats). As impaired dopamine D1 receptor (D₁R) function might play a role in the cognitive dysfunctions observed in patients with schizophrenia, the second goal of this study was to determine the brain-region-specific D₁R-mediated signaling, ligand binding, and mRNA expression. None of the treatments affected the behavior of the control animals significantly; however, the combination treatment enhanced D₁R binding and activation in the cerebral cortex. The Wisket rats exhibited impaired motivation, attention, and cognitive function, as well as a lower level of cortical D₁R binding, signaling, and gene expression. Clozapine caused further deterioration of the behavioral parameters, without a significant effect on the D₁R system. Metformin blunted the clozapine-induced impairments, and, similarly to that observed in the control animals, increased the functional activity of D₁R. This study highlights the beneficial effects of metformin (at the behavioral and cellular levels) in blunting clozapine-induced adverse effects.

Impact cérébral structurel et fonctionnel de la Clozapine chez les patients souffrant de schizophrénie : revue systématique des études longitudinales en neuroimagerie

OBJECTIF

L'objectif de cette revue est d'identifier les corrélats anatomo-fonctionnels cérébraux lors d'un traitement par clozapine (CLZ) ainsi que les marqueurs anatomo-fonctionnels prédictifs de la réponse à la CLZ.

MÉTHODES

Nous avons réalisé une revue systématique de la littérature avec les bases de données MEDLINE et Web of Science afin d'identifier et d'examiner toutes les études longitudinales en neuroimagerie investiguant l'impact cérébral de la CLZ.

RÉSULTATS

30 études ont été incluses et analysées. La CLZ induit une diminution du volume et de la perfusion dans les noyaux gris centraux chez les patients répondeurs. Un plus grand volume de substance grise et perfusion dans ces structures avant l'instauration de la CLZ étaient associés à une meilleure réponse au traitement. La diminution de volume et de perfusion au niveau du cortex préfrontal (CPF) est observée malgré l'instauration de CLZ mais de façon moins importante chez les patients sous CLZ que chez les patients sous antipsychotiques typiques. Un plus grand volume au niveau du CPF avant l'instauration de la CLZ est associé à une meilleure réponse clinique dans la majorité des études. Enfin, la CLZ semble induire une réduction des altérations au niveau de la substance blanche.

CONCLUSION

Les corrélats anatomo-fonctionnels de la CLZ différent de ceux des autres antipsychotiques avec une action spécifique de la CLZ au niveau des ganglions de la base et du CPF pouvant participer à sa supériorité en termes de réponse clinique. Plusieurs données cliniques et d'imagerie conduisent à l'hypothèse d'un meilleur pronostic associé à une instauration plus rapide de la CLZ.

History of the dopamine hypothesis of antipsychotic action

The dopamine hypothesis of how antipsychotic drugs exert their beneficial effect in psychotic illness has an interesting history that dates back to 1950. This hypothesis is not to be confused with the dopamine hypothesis of schizophrenia; the aim of the latter is to explain the etiology of schizophrenia. The present review does not deal with schizophrenia but, rather, with the historical development of our current understanding of the dopamine-associated actions of the drugs that reduce the symptoms of psychosis. This historical review begins with the serendipitous discovery of chlorpromazine, a drug synthesized around a chemical core that initially served to produce man-made dyes. This molecular core subsequently contributed to the chemistry of antihistamines. It was with the aim of producing a superior antihistamine that chlorpromazine was synthesized; instead, it revolutionized the treatment of psychosis. The first hypothesis of how this drug worked was that it induced hypothermia, a cooling of the body that led to a tranquilization of the mind. The new, at the time, discoveries of the presence of chemical transmitters in the brain soon steered investigations away from a temperature-related hypothesis toward questioning how this drug, and other drugs with similar properties and effects, modulated endogenous neurotransmission. As a result, over the years, researchers from around the world have begun to progressively learn what antipsychotic drugs do in the brain.

Differentiating the effect of antipsychotic medication and illness on brain volume reductions in first-episode psychosis: A Longitudinal, Randomised, Triple-blind, Placebo-controlled MRI Study

Changes in brain volume are a common finding in Magnetic Resonance Imaging (MRI) studies of people with psychosis and numerous longitudinal studies suggest that volume deficits progress with illness duration. However, a major unresolved question concerns whether these changes are driven by the underlying illness or represent iatrogenic effects of antipsychotic medication. In this study, 62 antipsychotic-naïve patients with first-episode psychosis (FEP) received either a second-generation antipsychotic (risperidone or paliperidone) or a placebo pill over a treatment period of 6 months. Both FEP groups received intensive psychosocial therapy. A healthy control group (n = 27) was also recruited. Structural MRI scans were obtained at baseline, 3 months and 12 months. Our primary aim was to differentiate illness-related brain volume changes from medication-related changes within the first 3 months of treatment. We secondarily investigated long-term effects at the 12-month timepoint. From baseline to 3 months, we observed a significant group x time interaction in the pallidum (p < 0.05 FWE-corrected), such that patients receiving antipsychotic medication showed increased volume, patients on placebo showed decreased volume, and healthy controls showed no change. Across the entire patient sample, a greater increase in pallidal grey matter volume over 3 months was associated with a greater reduction in symptom severity. Our findings indicate that psychotic illness and antipsychotic exposure exert distinct and spatially distributed effects on brain volume. Our results align with prior work in suggesting that the therapeutic efficacy of antipsychotic medications may be primarily mediated through their effects on the basal ganglia.

Discovery of Nonracemic Amisulpride to Maximize Benefit/Risk of 5-HT7 and D2 Receptor Antagonism for the Treatment of Mood Disorders

In contrast to the dose‐occupancy relationship in the treatment of schizophrenia, the minimal effective level of dopamine receptor 2 (D2R) blockade for antipsychotics in the treatment of bipolar depression is unknown. Lower doses aimed at reducing extrapyramidal side effects must be balanced against the need to retain the therapeutic benefit of D2R blockade on emergent cycling, mixed, manic, anxiety, and/or psychotic symptoms. Dose‐reductions intended to lower D2R blockade, however, could also decrease concomitant serotonin receptor antagonism and its potential benefit on depressive symptoms. Here, we uncoupled the potential antidepressant activity in amisulpride, driven by 5‐HT7 receptor (5‐HT7R) antagonism, from the D2R‐mediated antipsychotic activity by discovering that each enantiomer favors a different receptor. Aramisulpride was more potent at 5‐HT7R relative to esamisulpride (Ki 47 vs. 1,900 nM, respectively), whereas esamisulpride was more potent at D2R (4.0 vs. 140 nM). We hypothesized that a nonracemic ratio might achieve greater 5‐HT7R‐mediated antidepressant effects at a lower level of D2R blockade. The dose‐occupancy relationship of esamisulpride at D2R was determined by positron emission tomography (PET) imaging in human volunteers. Separately the dose‐relationship of aramisulpride was established in humans using suppression of rapid eye movement (REM) sleep as a marker of 5‐HT7R antagonism. These results led to the discovery of an 85:15 ratio of aramisulpride to esamisulpride (SEP‐4199) that maximizes the potential for antidepressant benefit of aramisulpride via 5‐HT7R and reduces esamisulpride to minimize D2R‐related extrapyramidal side effects while still retaining D2R‐mediated effects predicted to provide benefit in bipolar depression. The antidepressant efficacy of SEP‐4199 was recently confirmed in a proof‐of‐concept trial for the treatment of bipolar depression (NCT03543410).

Regional brain network and behavioral alterations in EGR3 gene transfected rat model of schizophrenia

Schizophrenia is a severe psychiatric disease while its etiology and effective treatment are not completely clear. A rat model of schizophrenia was previously established by transfecting EGR3 gene into the hippocampus of rats. This study aimed to investigate the behavioral and cerebral alterations of the schizophrenic model rats and the risperidone effects. Twenty-six rats were divided into 3 groups: schizophrenia model group (E group), risperidone treatment group (T group), and healthy control group (H group). Morris water maze and open field test were used as behavioral tests, resting-state functional magnetic resonance imaging (fMRI) was performed after EGR3 gene transfection and risperidone therapy. Graph analyses were used for examining cerebral alterations of the rats. Behavioral tests demonstrated reduced spatial working memory and exploring unfamiliar space ability in schizophrenic model rats. Graph analyses revealed reduced regional architectures in the olfactory bulb, nucleus accumbens, and pineal gland in group E compared to group H (p < 0.05), while group T showed increased regional architecture in pineal gland compared to group E (p < 0.05). Besides, the regional architectures in the olfactory bulb, nucleus accumbens were lower in group T than group H, while the hippocampus showed increased regional architecture in group T compared to group H (p < 0.05). Schizophrenia induced several regional alterations in the cerebrum while risperidone can reverse part of these alterations. This study lends support for future research on the pathology of schizophrenia and provides new insights on the role of risperidone in schizophrenia.

Effect of CYP2D6 polymorphisms on plasma concentration and therapeutic effect of risperidone

BACKGROUND

This study aimed to investigate the influence of CYP2D6 polymorphisms on risperidone plasma concentrations in patients with schizophrenia. Based on pharmacogenomics, we examined whether plasma concentration of risperidone is associated with clinical response and adverse side-effects.

METHODS

We recruited patients with chronic schizophrenia who were then treated with risperidone. The CYP2D6 genotypes were determined using targeted sequencing. All high-frequency mutation sites of the nine exons of the gene were assayed in the present study. Plasma concentrations of risperidone and 9-hydroxyrisperidone (9-OH-RIS) were measured using high-performance liquid chromatography (HPLC). Psychiatric symptoms were monitored using The Positive and Negative Syndrome Scale (PANSS), Brief Psychiatric Rating Scale (BPRS), and Clinical Global Impression (CGI). Adverse effects were evaluated using the Barnes Akathisia Scale (BAS) and Extrapyramidal Symptom Rating Scale (ESRS). Follow-up visits were scheduled at weeks 2,4, and 8 after treatment initiation.

RESULTS

Among the 76 patients, 100 C > T (rs1065852), 1038 C > T (rs1081003), 1662 G > C (rs1058164), 2851 C > T (rs16947), and 4181G > C (rs1135840) variants were detected. The most common allele was CYP2D6*10 (81.6%), whereas CYP2D6*2 (9.2%) and CYP2D6*5 (17.1%) were relatively rare. Plasma levels of risperidone and the risperidone/9-OH risperidone ratio (R/9-OH) were significantly increased in individuals with CYP2D6*10 (P < 0.05). The change in PANSS score, weight, high-density lipoprotein (HDL) level, prolactin (PRL) level, and ESRS were significantly different from baseline, between the different genotypes (P < 0.01). Moreover, individuals with CYP2D6*10 homozygous (TT) mutations were associated with higher risperidone concentration and R/9-OH ratio than those with heterozygous mutations (CT) (P < 0.01). A change from baseline in BPRS scores was observed only during week 8 and was different between heterozygous and homozygous mutations. As for the C2851T polymorphism, the incidence of adverse metabolic effects was significantly different between the C/C and C/T genotypes (P < 0.01). Regarding the G4181C polymorphisms, the changes from baseline in GLU and TG, were different between the C/C and C/G genotypes (P < 0.01).

CONCLUSIONS

The genotype of CYP2D6 significantly influences the plasma concentration of risperidone and may subsequently influence the adverse side-effects following risperidone treatment, while also exerting a slight influence on clinical outcomes.

Outcomes in treatment-resistant schizophrenia: symptoms, function and clozapine plasma concentrations

BACKGROUND

Clozapine is the only medication licenced for treating patients with treatment-refractory schizophrenia. However, there are no evidence-based guidelines as to the optimal plasma level of clozapine to aim for, and their association with clinical and functional outcome.

OBJECTIVE

We assessed the relationship between clinical and functional outcome measures and blood concentrations of clozapine among patients with treatment-refractory psychosis.

METHODS

Data were reviewed in 82 patients with treatment-refractory psychosis admitted to a specialised tertiary-level service and treated with clozapine. Analysis focussed on the relationship between clozapine and norclozapine plasma concentrations and the patient's clinical symptoms and functional status.

RESULTS

Clinical symptom improvement was positively correlated with norclozapine plasma concentrations and inversely correlated with clozapine to norclozapine plasma concentrations ratio. Clozapine concentrations showed a bimodal association with clinical improvement (peaks around 350 and 660 ng/ml). Clinical symptom improvement correlated with functional outcomes, although there was no significant correlation between the latter and clozapine or norclozapine plasma concentrations.

CONCLUSION

Clozapine treatment was associated with optimal clinical improvement at two different peak plasma concentrations around 350 and 650 ng/ml. Clinical improvement was associated with functional outcome; however, functionality was not directly associated with clozapine concentrations. A subset of patients may require higher clozapine plasma concentrations to achieve clinical improvement.

Translational medicine of the glutamate AMPA receptor

Psychiatric and neurological disorders severely hamper patient's quality of life. Despite their high unmet needs, the development of diagnostics and therapeutics has only made slow progress. This is due to limited evidence on the biological basis of these disorders in humans. Synapses are essential structural units of neurotransmission, and neuropsychiatric disorders are considered as "synapse diseases". Thus, a translational approach with synaptic physiology is crucial to tackle these disorders. Among a variety of synapses, excitatory glutamatergic synapses play central roles in neuronal functions. The glutamate α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) is a principal component of glutamatergic neurotransmission; therefore, it is considered to be a promising translational target. Here, we review the limitations of current diagnostics and therapeutics of neuropsychiatric disorders and advocate the urgent need for the promotion of translational medicine based on the synaptic physiology of AMPAR. Furthermore, we introduce our recent translational approach to these disorders by targeting at AMPARs.

Association of clozapine-related metabolic disturbances with CYP3A4 expression in patients with schizophrenia

Clozapine is effective in treatment-resistant schizophrenia; however, adverse effects often result in discontinuation of clozapine therapy. Many of the side-effects are associated with pharmacokinetic variations; therefore, the expression of major clozapine-metabolizing enzymes (CYP1A2, CYP3A4) in patients may predict development of adverse effects. In patients with schizophrenia (N = 96), development of clozapine concentration-dependent metabolic side-effects was found to be associated with pharmacokinetic variability related to CYP3A4 but not to CYP1A2 expression. In low CYP3A4 expressers, significant correlation was detected between fasting glucose level and clozapine concentration; moreover, the incidence of abnormal glucose level was associated with exaggerated clozapine concentrations (> 600 ng/ml). In low CYP3A4 expressers, exaggerated concentrations were more frequently observed than in normal/high expressers. Moderate/high risk obesity (BMI ≥ 35) more frequently occurred in low CYP3A4 expresser patients than in normal/high expressers. In patients with normal/high CYP3A4 expression and consequently with extensive clozapine-metabolizing capacity, norclozapine/clozapine ratio correlated with fasting glucose levels, triglyceride concentrations and BMI. Low CYP3A4 expression often resulting in exaggerated clozapine concentrations was considered to be as an important risk factor for some concentration-dependent adverse effects as normal/high CYP3A4 expression evoking high norclozapine/clozapine ratios. CYP3A4-status can identify patients with increased risk for metabolic side-effects and prevent their development by careful therapeutic strategy.

A positron emission tomography occupancy study of brexpiprazole at dopamine D2 and D3 and serotonin 5-HT1A and 5-HT2A receptors, and serotonin reuptake transporters in subjects with schizophrenia

The objective of this study (NCT01854944) was to assess D2/D3, 5-HT1A, 5-HT2A and serotonin transporter (SERT) occupancies of brexpiprazole in adult subjects with schizophrenia in order to identify the in vivo pharmacologic profile that may be relevant to the antipsychotic, antidepressant, and side effect profiles of the drug. Subjects were grouped into three independent cohorts of four subjects each. All subjects underwent positron emission tomography (PET) scans with two different radiotracers at baseline prior to brexpiprazole administration, and again on Day 10 after daily doses of either 4 mg (Cohorts 1 and 2), or 1 mg (Cohort 3). Cohort 1 received scans with [11C]-(+)-PHNO to measure D2 and D3 receptor occupancy and [11C]CUMI101 to measure 5-HT1A occupancy; Cohort 2 received [11C]MDL100907 for 5-HT2A occupancy and [11C]DASB for SERT occupancy; Cohort 3 underwent scanning with [11C]-(+)-PHNO and [11C]MDL100907. Five female and seven male subjects, aged 42 ± 8 years (range, 28-55 years), participated in this study. Dose dependency was observed at D2 receptors, with occupancies reaching 64 ± 8% (mean +/- SD) following 1 mg/day and 80 ± 12% following 4 mg/day. D3 receptor availability increased following 1 mg brexpiprazole treatment and did not change with 4 mg. Robust and dose-related occupancy was also observed at 5-HT2A receptors. Negligible occupancy (<5%) was observed at 5-HT1A and SERT at 4 mg/day. In summary, brexpiprazole demonstrated in vivo binding to D2 receptors and 5-HT2A receptors at steady state after 10 days of daily administration in a dose dependent manner, while binding to D3, 5-HT1A receptors and SERT was not detectable with the radiotracers used for these targets. This pharmacologic profile is consistent with the observed antipsychotic and antidepressant effects.

Immunoendocrine Peripheral Effects Induced by Atypical Antipsychotics

Atypical antipsychotics (AAP) or second-generation antipsychotics are the clinical option for schizophrenia treatment during acute psychoses, but they are also indicated for maintenance during lifetime, even though they are being used for other psychiatric conditions in clinical practice such as affective disorders and autism spectrum disorder, among others. These drugs are differentiated from typical antipsychotics based on their clinical profile and are a better choice because they cause fewer side effects regarding extrapyramidal symptoms (EPS). Even though they provide clear therapeutic benefits, AAP induce peripheral effects that trigger phenotypic, functional, and systemic changes outside the Central Nervous System (CNS). Metabolic disease is frequently associated with AAP and significantly impacts the patient's quality of life. However, other peripheral changes of clinical relevance are present during AAP treatment, such as alterations in the immune and endocrine systems as well as the intestinal microbiome. These less studied alterations also have a significant impact in the patient's health status. This manuscript aims to revise the peripheral immunological, endocrine, and intestinal microbiome changes induced by AAP consumption recommended in the clinical guidelines for schizophrenia and other psychiatric disorders.

Samidorphan mitigates olanzapine-induced weight gain and metabolic dysfunction in rats and non-human primates

BACKGROUND

Olanzapine, regarded as one of the most efficacious antipsychotic medications for the treatment of schizophrenia, is associated with a high risk of weight gain and metabolic dysfunction. ALKS 3831, a clinical candidate for treatment of schizophrenia, is a combination of olanzapine and samidorphan, an opioid receptor antagonist. The addition of samidorphan is intended to mitigate weight gain and the metabolic dysregulation associated with the use of olanzapine.

METHODS

Non-clinical studies were conducted to assess the metabolic effects of olanzapine and samidorphan alone and in combination at clinically relevant exposure levels.

RESULTS

Chronic olanzapine administration in male and female rats shifted body composition by increasing adipose mass, which was accompanied by an increase in the rate of weight gain in female rats. Co-administration of samidorphan normalized body composition in both sexes and attenuated weight gain in female rats. In hyperinsulinemic euglycemic clamp experiments conducted prior to measurable changes in weight and/or body composition, olanzapine decreased hepatic insulin sensitivity and glucose uptake in muscle while increasing uptake in adipose tissue. Samidorphan appeared to normalize glucose utilization in both tissues, but did not restore hepatic insulin sensitivity. In subsequent studies, samidorphan normalized olanzapine-induced decreases in whole-body glucose clearance following bolus insulin administration. Results from experiments in female monkeys paralleled the effects in rats.

CONCLUSIONS

Olanzapine administration increased weight gain and adiposity, both of which were attenuated by samidorphan. Furthermore, the combination of olanzapine and samidorphan prevented olanzapine-induced insulin insensitivity. Collectively, these data indicate that samidorphan mitigates several metabolic abnormalities associated with olanzapine in both the presence and the absence of weight gain.

Clinical Course, Neurobiology and Therapeutic Approaches to Treatment Resistant Schizophrenia. Toward an Integrated View

Despite considerable psychotherapeutic advancement since the discovery of chlorpromazine, almost one third of patients with schizophrenia remain resistant to dopamine-blocking antipsychotics, and continue to be exposed to unwanted and often disabling side effects, but little if any clinical benefit. Even clozapine, the superior antipsychotic treatment, is ineffective in approximately half of these patients. Thus treatment resistant schizophrenia (TRS), continues to present a major therapeutic challenge to psychiatry. The main impediment to finding novel treatments is the lack of understanding of precise molecular mechanisms leading to TRS. Not only has the neurobiology been enigmatic for decades, but accurate and early detection of patients who are at risk of not responding to dopaminergic blockade remains elusive. Fortunately, recent work has started to unravel some of the neurobiological mechanisms underlying treatment resistance, providing long awaited answers, at least to some extent. Here we focus on the scientific advances in the field, from the clinical course of TRS to neurobiology and available treatment options. We specifically emphasize emerging evidence from TRS imaging and genetic literature that implicates dysregulation in several neurotransmitters, particularly dopamine and glutamate, and in addition genetic and neural alterations that concertedly may lead to the formation of TRS. Finally, we integrate available findings into a putative model of TRS, which may provide a platform for future studies in a bid to open the avenues for subsequent development of effective therapeutics.

Cross-tolerance between nitric oxide synthase inhibition and atypical antipsychotics modify nicotinamide-adenine-dinucleotide phosphate-diaphorase activity in mouse lateral striatum

Previous research indicates that the subchronic administration of NG-nitro-L-arginine (L-NOARG) produces tolerance to haloperidol-induced catalepsy in Swiss mice. The present study aimed to further investigate whether intermittent subchronic systemic administration of L-NOARG induces tolerance to the cataleptic effects of haloperidol as well as olanzapine or clozapine (Clz) in C57Bl mice after subchronic administration for 5 consecutive days. Striatal FosB protein expression was measured in an attempt to gain further insights into striatal mechanisms in antipsychotic-induced extrapyramidal symptoms side effects. An nicotinamide-adenine-dinucleotide phosphate-diaphorase histochemical reaction was also used to investigate whether tolerance could induce changes in the number of nitric oxide synthase-active neurons. Subchronic administration of all antipsychotics produced catalepsy, but cross-tolerance was observed only between L-NOARG (15 mg/kg, intraperitoneally) and Clz (20 mg/kg, intraperitoneally). This cross-tolerance effect was accompanied by decreased FosB protein expression in the dorsal striatum and the nucleus accumbens shell region, and reduced icotinamide-adenine-dinucleotide phosphate-diaphorase activity in the dorsal and ventral lateral striatum. Overall, these results suggest that interference with the formation of nitric oxide, mainly in the dorsal and ventral lateral-striatal regions, appears to improve the cataleptic effects induced by antipsychotics acting as antagonists of low-affinity dopamine D2 receptor, such as Clz.

Antipsychotics: Mechanisms underlying clinical response and side-effects and novel treatment approaches based on pathophysiology

Antipsychotic drugs are central to the treatment of schizophrenia and other psychotic disorders but are ineffective for some patients and associated with side-effects and nonadherence in others. We review the in vitro, pre-clinical, clinical and molecular imaging evidence on the mode of action of antipsychotics and their side-effects. This identifies the key role of striatal dopamine D2 receptor blockade for clinical response, but also for endocrine and motor side-effects, indicating a therapeutic window for D2 blockade. We consider how partial D2/3 receptor agonists fit within this framework, and the role of off-target effects of antipsychotics, particularly at serotonergic, histaminergic, cholinergic, and adrenergic receptors for efficacy and side-effects such as weight gain, sedation and dysphoria. We review the neurobiology of schizophrenia relevant to the mode of action of antipsychotics, and for the identification of new treatment targets. This shows elevated striatal dopamine synthesis and release capacity in dorsal regions of the striatum underlies the positive symptoms of psychosis and suggests reduced dopamine release in cortical regions contributes to cognitive and negative symptoms. Current drugs act downstream of the major dopamine abnormalities in schizophrenia, and potentially worsen cortical dopamine function. We consider new approaches including targeting dopamine synthesis and storage, autoreceptors, and trace amine receptors, and the cannabinoid, muscarinic, GABAergic and glutamatergic regulation of dopamine neurons, as well as post-synaptic modulation through phosphodiesterase inhibitors. Finally, we consider treatments for cognitive and negative symptoms such dopamine agonists, nicotinic agents and AMPA modulators before discussing immunological approaches which may be disease modifying. This article is part of the issue entitled 'Special Issue on Antipsychotics'.

Obsessive-Compulsive Symptoms in Schizophrenia: an Up-To-Date Review of Literature

PURPOSE OF REVIEW

This review will aim to summarize the current body of epidemiological, clinical and therapeutic knowledge concerning specific co-occurrence of obsessive-compulsive symptoms (OCSs) and schizophrenia spectrum disorder.

RECENT FINDINGS

Almost 30% of the patients with schizophrenia display OCS, and three main contexts of emergence are identified: prodromal symptoms of schizophrenia, co-occurrence of OCS and schizophrenia and antipsychotics-induced OCS. Recent clinical studies show that patients with SZ and OCS have more severe psychotic and depressive symptoms, higher suicidality and lower social functioning. A recent cognitive investigation found that OCS and delusions share specific metacognitive profiles, particularly through a heightened need to control thoughts. Finally, a recent cross-sectional study of clozapine-induced OCS found a dose-response relationship between clozapine and OCS. OCS appeared reliably as linked to poorer outcomes among patients with schizophrenia. However, the specific clinical value of OCS among other prodromal symptoms of schizophrenia remains unknown.

Effect of CYP2D6 genotype on exposure and efficacy of risperidone and aripiprazole: a retrospective, cohort study

BACKGROUND

The polymorphic CYP2D6 enzyme metabolises the antipsychotic drugs risperidone and aripiprazole to their active metabolites, 9OH-risperidone and dehydroaripiprazole. The aim of this study was to quantify the effect of CYP2D6 genetic variability on risperidone and aripiprazole exposure and treatment in a large patient population.

METHODS

We retrospectively obtained patient data from a routine therapeutic drug monitoring database at the Center for Psychopharmacology, Diakonhjemmet Hospital, Oslo, Norway, between Jan 1, 2005, and Oct 15, 2018. Individuals included in our analyses were CYP2D6-genotyped patients treated with risperidone or aripiprazole. Inclusion criteria for measurement of pharmacokinetic parameters (drug and metabolite serum concentrations) were oral administration of risperidone or aripiprazole, information known about prescribed daily dose and comedications, and aged older than 18 years. Exclusion criteria included polypharmacy with drugs known to be CYP2D6 inhibitors or CYP3A4 inducers or inhibitors. Treatment failure was analysed in all patients treated with risperidone or aripiprazole without these criteria. The first endpoint in our analysis was the metabolism of risperidone to 9OH-risperidone and aripiprazole to dehydroaripiprazole, estimated by the log-transformed ratio between the concentrations of metabolite and parent drug (ie, the metabolic ratio for risperidone [9OH-risperidone]/[risperidone] and the metabolic ratio for aripiprazole [dehydroaripiprazole]/[aripiprazole]). Endpoint two was measurement of drug exposure, quantified by the dose-normalised sum of parent drug and active metabolite serum concentrations (ie, active moiety). The third endpoint of treatment failure was measured as the number of patients switched from risperidone or aripiprazole to another antipsychotic drug within 1 year after the last therapeutic drug monitoring analysis of risperidone or aripiprazole. Patient subgroups were defined by CYP2D6 genotype-determined metaboliser status: poor metabolisers, intermediate metabolisers, normal metabolisers, and ultrarapid metabolisers. ANOVA was used to assess the differences in metabolic ratios, active moieties, and daily doses between individual metaboliser categories, and risperidone and aripiprazole therapeutic failures were compared by logistic regression using the normal metaboliser subgroup as a reference.

FINDINGS

1288 risperidone-treated patients and 1334 aripiprazole-treated patients were included in the study, of whom 725 (56%) risperidone-treated and 890 (67%) aripiprazole-treated patients were eligible for the pharmacokinetic analyses. CYP2D6 genotype significantly changed risperidone and aripiprazole metabolism resulting in an approximately 1·6-times and 1·4-times increase in risperidone and aripiprazole active moiety exposure in poor and intermediate metabolisers compared with normal metabolisers, respectively (odds ratios [OR] for the risperidone dose-normalised active moiety concentration 1·568, 95% CI 1·401-1·736, and 1·373, 1·213-1·532; and for the aripiprazole dose-normalised active moiety concentration 1·585, 1·447-1·724, and 1·476, 1·263-1·688, respectively; p<0·0001 for all). Compared with doses for normal metabolisers, clinicians reduced daily doses of risperidone and aripiprazole administered to poor metabolisers by 19% (95% CI 5-35, p=0·010) and 15% (95% CI 1-28, p=0·033) respectively. The incidence of switching from risperidone to another antipsychotic was increased in ultrarapid metabolisers (OR 2·934, 95% CI 1·437-5·989, p=0·003) and poor metabolisers (1·874, 1·128-3·112, p=0·015); by contrast, the incidence of switching from aripiprazole to another antipsychotic was not significantly related to CYP2D6 metaboliser status.

INTERPRETATION

CYP2D6 genotype had a substantial clinical effect on risperidone and aripiprazole exposure and on the therapeutic failure of risperidone. Pre-emptive CYP2D6 genotyping would be valuable for individualising risperidone and aripiprazole dosing and treatment optimisation.

FUNDING

H2020 program U-PGx, The Swedish Research Council, the Swedish Brain foundation, and the South-Eastern Norway Regional Health Authority.

Interaction between childhood adversity and functional polymorphisms in the dopamine pathway on first-episode psychosis

BACKGROUND

There is consistent evidence of a cumulative relationship between childhood adversity and psychosis, with number of adversities experienced increasing the probability of psychosis onset. It is possible that genetic factors moderate the association between childhood adversity and psychosis, potentially by influencing how an individual reacts biologically and/or psychologically following exposure to adversity, in such a way as to set them off on the path to psychosis. However, identifying the specific genetic variants involved and how they interact with childhood adversity remains challenging. We examined whether the association between cumulative exposure to childhood adversity and development of psychotic disorder was moderated by the COMT Val¹⁵⁸Met, AKT1 rs2494732 or DRD2 rs1076560 polymorphisms, known to affect dopamine levels.

METHODS

Participants were 285 first-presentation psychosis cases and 256 geographically-matched controls drawn from the Genetics and Psychosis (GAP) study. Childhood adversity was assessed using the Childhood Experience of Care and Abuse Questionnaire (CECA.Q) and blood- and cheek-derived genotype data were collected.

RESULTS

Our findings revealed no main effect of COMT Val¹⁵⁸Met, AKT1 rs2494732 and DRD2 rs1076560 polymorphisms on psychosis case status or reports of childhood adversity. Individuals reporting a history of multiple adversities were more likely to be psychosis patients than controls, regardless of their genetic risk. There was no evidence of candidate genotype by childhood adversity interactions in relation to psychosis onset.

CONCLUSION

These findings did not provide evidence of a possible role of COMT Val¹⁵⁸Met, AKT1 rs2494732 or DRD2 rs1076560 genotypes in modifying the association between childhood adversity and onset of psychosis.

Early Identification and Intervention of Schizophrenia: Insight From Hypotheses of Glutamate Dysfunction and Oxidative Stress

Schizophrenia is a severe mental disorder which leads to functional deterioration. Early detection and intervention are vital for better prognosis. However, the diagnosis of schizophrenia still depends on clinical observation to date. Without reliable biomarkers, schizophrenia is difficult to detect in its early phase. Further, there is no approved medication for prodromal schizophrenia because current antipsychotics fail to show satisfactory efficacy and safety. Therefore, to develop an effective early diagnostic and therapeutic approach for schizophrenia, especially in its prodromal phase, is crucial. Glutamate signaling dysfunction and dysregulation of oxidative stress have been considered to play important roles in schizophrenic prodrome. The N-methyl-D-aspartate receptor (NMDAR) is one of three types of ionotropic glutamate receptors. In this article, we reviewed literature regarding NMDAR hypofunction, oxidative stress, and the linkage between both in prodromal schizophrenia. The efficacy of NMDAR enhancers such as D-amino acid oxidase inhibitor was addressed. Finally, we highlighted potential biomarkers related to NMDAR and oxidative stress regulation, and therefore suggested the strategies of early detection and intervention of prodromal schizophrenia. Future larger-scale studies combining biomarkers and novel drug development for early psychosis are warranted.

Dopamine D2 receptor occupancy of lumateperone (ITI-007): a Positron Emission Tomography Study in patients with schizophrenia

Dopamine D₂ receptor occupancy (D₂RO) is a key feature of all currently approved antipsychotic medications. However, antipsychotic efficacy associated with high D₂RO is often limited by side effects such as motor disturbances and hyperprolactinemia. Lumateperone (ITI-007) is a first-in-class selective and simultaneous modulator of serotonin, dopamine and glutamate in development for the treatment of schizophrenia and other disorders. The primary objective of the present study was to determine D₂RO at plasma steady state of 60 mg ITI-007, a dose that previously demonstrated antipsychotic efficacy in a controlled trial, administered orally open-label once daily in the morning for two weeks in patients with schizophrenia (N = 10) and after at least a two-week washout period from standard of care antipsychotics. D₂RO was determined using positron emission tomography with ¹¹C-raclopride as the radiotracer. Mean peak dorsal striatal D₂RO was 39% at 60 mg ITI-007 occurring 1 h post-dose. Lumateperone was well-tolerated with a favorable safety profile in this study. There were no clinically significant changes in vital signs, ECGs, or clinical chemistry laboratory values, including prolactin levels. There were no adverse event reports of akathisia or other extrapyramidal motor side effects; mean scores on motor function scales indicated no motor disturbances with lumateperone treatment. This level of occupancy is lower than most other antipsychotic drugs at their efficacious doses and likely contributes to the favorable safety and tolerability profile of lumateperone with reduced risk for movement disorders and hyperprolactinemia. If approved, lumateperone may provide a new and safe treatment option for individuals living with schizophrenia.

Hypofunctional Dopamine Uptake and Antipsychotic Treatment-Resistant Schizophrenia

Antipsychotic treatment resistance in schizophrenia remains a major issue in psychiatry. Nearly 30% of patients with schizophrenia do not respond to antipsychotic treatment, yet the underlying neurobiological causes are unknown. All effective antipsychotic medications are thought to achieve their efficacy by targeting the dopaminergic system. Here we review early literature describing the fundamental mechanisms of antipsychotic drug efficacy, highlighting mechanistic concepts that have persisted over time. We then reconsider the original framework for understanding antipsychotic efficacy in light of recent advances in our scientific understanding of the dopaminergic effects of antipsychotics. Based on these new insights, we describe a role for the dopamine transporter in the genesis of both antipsychotic therapeutic response and primary resistance. We believe that this discussion will help delineate the dopaminergic nature of antipsychotic treatment-resistant schizophrenia.

Optimization of maintenance therapy of Risperidone with CYP2D6 genetic polymorphisms through an extended translational framework-based prediction of target occupancies/clinical outcomes

Risperidone, one of the second-generation antipsychotics, can efficiently target dopamine D₂ and serotonin 5-HT_2A receptors. There actually exists significant implication of CYP2D6 genetic polymorphisms on the metabolic kinetics of risperidone, little is known about the extent of CYP2D6 impacting human D2 and 5-HT2A receptor occupancies as well as the clinical efficacy and efficacy in schizophrenia treatment. Here we assessed the influences of CYP2D6 gene polymorphisms on human target occupancies/clinical outcomes and optimized the maintenance therapy of risperidone. A translational framework, previously developed using in vitro and in vivo information in rats, was used as the basis for integrating the effects of CYP2D6 genetic polymorphisms on target occupancies and clinical outcomes. D₂ occupancy as a biomarker was related to Positive and Negative Syndrome Scale (PANSS) response and Simpson-Angus Scale (SAS). The population approach was applied to characterize pharmacokinetic and pharmacodynamic (PK/PD) profiles of risperidone. Non-compartment analysis method was performed to calculate the steady state PK/PD parameters of both risperidone and 9-hydroxyrisperidone. The predictive power of this extended translational framework was determined by comparing the predictions of target occupancies and clinical outcomes with the reported human values of risperidone at clinically suggested dosage of 4.0 mg/day. This extended translational framework was adequately used to predict human target occupancies and clinical outcomes. At the steady state, D₂ ROs were 75.8%, 79.3% and 86.0% for CYP2D6 poor metabolizer (PM), intermediate metabolizer (IM) and extensive metabolizer (EM), respectively; 5-HT_2A ROs were 96.4%, 97.2% and 98.4% for CYP2D6 PM, IM and EM, respectively; PANSS changes from placebo were -5.3, -7.7 and -11.3 for CYP2D6 PM, IM and EM, respectively; SAS changes from placebo were 0.13, 0.15 and 0.18 for CYP2D6 PM, IM and EM, respectively. The predictions of human D₂, 5-HT_2A RO, PANSS and SAS changes for risperidone with CYP2D6 genetic polymorphisms were well in line with the reported values in clinic. 5.0, 4.0 and 2.5 mg/day were the equivalent dosages of risperidone for CYP2D6 PM, IM and EM, respectively. The optimized maintenance therapy of risperidone was provided through the Three-Step method and the dosage range was 2.5-5.0 mg/day for three CYP2D6 gene groups in the present study. Taken together, our findings demonstrate that this extended translational framework not only differentiates the effects of CYP2D6 genetic polymorphisms on target occupancies and clinical outcomes, but also constitutes a scientific basis to optimize the maintenance therapy of neuropsychiatric patients in clinic.

Classics in Chemical Neuroscience: Risperidone

After the identification of the influence of serotonergic receptors in ameliorating the negative symptoms associated with schizophrenia, atypical antipsychotics were developed by incorporating dopamine and serotonin antagonism. Risperidone, sold under the trade name Risperdal, was the second atypical antipsychotic developed following clozapine but quickly became a first-line treatment for acute and chronic schizophrenia because of its preferential side effect profile. Despite initial Food and Drug Administration approval 25 years ago, risperidone continues to be a fundamental treatment for schizophrenia, bipolar I disorder, and autism-related irritability. It is on the World Health Organization's List of Essential Medicines for its balance of efficacy, safety, tolerability, and cost-effectiveness. In this review, we highlight the history and importance of risperidone as an atypical antipsychotic, in addition to its chemical synthesis, manufacturing, drug metabolism and pharmacokinetics, pharmacology, structure-activity relationship, indications, and adverse effects.

Review of serum prolactin levels as an antipsychotic-response biomarker

Antipsychotics acting as antagonists at dopamine D2 receptors concentrated in the striatum are the cornerstone of effective treatment of psychosis. Substantial progress in treating persons with schizophrenia could be achieved by the identification of biomarkers which reliably determine the lowest efficacious dose of antipsychotics. Prolactin levels have been considered a promising treatment-response biomarker due to dopamine’s regulation of serum prolactin levels through D2 receptors in the hypothalamic-pituitary pathway. Prolactin secretion in response antipsychotic administration is associated with the antipsychotics affinity for D2 receptors. This review assesses the available literature on the use of serum prolactin levels as an antipsychotic-response biomarker. Articles were identified through PubMed as well as the reference lists of full text articles available online. Relevant publications were summarized briefly to define the limitations and utility of serum prolactin levels as a tool for improving antipsychotic dosing. Serum prolactin levels in combination with prolactin-inducing potencies for each antipsychotic may help identify the lowest effective dose of antipsychotic medications. , In addition to the fact that prolactin secretion is dependent on serum antipsychotic levels and not brain levels, recent findings show that prolactin release is independent of the β-arrestin-2 pathway and GSK3β regulation, one branch of the pathway that has been implicated in antipsychotic efficacy. Therefore, serum prolactin is an indirect biomarker for treatment response. Further investigations are warranted to characterize prolactin-antipsychotic dose-response curves and systematically test the utility of measuring prolactin levels in patients to identify a person’s lowest efficacious dose.

Oral haloperidol or olanzapine intake produces distinct and region-specific increase in cannabinoid receptor levels that is prevented by high fat diet

Clinical studies show higher levels of cannabinoid CB1 receptors (CB1R) in the brain of schizophrenic patients while preclinical studies report a significant functional interaction between dopamine D2 receptors and CB1Rs as well as an upregulation of CB1Rs after antipsychotic treatment. These findings prompted us to study the effects of chronic oral intake of a first and a second generation antipsychotic, haloperidol and olanzapine, on the levels and distribution of CB1Rs in the rat brain. Rats consumed either regular chow or high-fat food and drank water, haloperidol drinking solution (1.5mg/kg), or olanzapine drinking solution (10mg/kg) for four weeks. Motor and cognitive functions were tested at the end of treatment week 3 and upon drug discontinuation. Two days after drug discontinuation, rats were euthanized and brains were processed for in vitro receptor autoradiography. In chow-fed animals, haloperidol and olanzapine increased CB1R levels in the basal ganglia and the hippocampus, in a similar, but not identical pattern. In addition, olanzapine had unique effects in CB1R upregulation in higher order cognitive areas, in the secondary somatosensory cortex, in the visual and auditory cortices and the geniculate nuclei, as well as in the hypothalamus. High fat food consumption prevented antipsychotic-induced increase in CB1R levels in all regions examined, with one exception, the globus pallidus, in which they were higher in haloperidol-treated rats. The results point towards the hypothesis that increased CB1R levels could be a confounding effect of antipsychotic medication in schizophrenia that is circumveneted by high fat feeding.

A pharmacodynamic modelling and simulation study identifying gender differences of daily olanzapine dose and dopamine D2-receptor occupancy

BACKGROUND

Gender differences in treatment response rates for patients treated with antipsychotics are known. However, the literature lacks a pharmacodynamic model to allow for gender-based clinical trial simulations from modelling parameters for Olanzapine and dopamine D2 receptor occupancy. Thus, the primary aim of this analysis is to test and quantify the effect of gender on the pharmacodynamics of Olanzapine.

METHODS

Population pharmacodynamic modelling was performed using non-linear mixed effects modelling in MONOLIX, while the Clinical Trial Simulations were performed using R for statistical programming. The pharmacometric analysis is based on a pooled data approach from three clinical studies where patients were diagnosed with schizophrenia and one clinical study where the patients were diagnosed with bipolar disorder.

RESULTS

Olanzapine D2RO was modelled using an Emax model in a study population of 70 patients. Population pharmacodynamic parameters were estimated to be: Emax = 85.6% (RSE = 3%), ED50-Men = 5.15 mg/day (RSE = 14) and ED50-Women = 2.38 mg/day (RSE = 34%), with the p-value = 0.037 for the gender-stratified ED50 results.

CONCLUSION

The pharmacometrics analysis and model-based dosing simulations suggest that, in order to achieve 70% D2RO, women require a 10 mg/day dose and men require approximately a 20 mg/day dose of Olanzapine. Further, clinical implications exist suggesting that clinicians should factor patient gender when considering both a starting dose, as well a, a maintenance dose for patients prescribed Olanzapine due to quantifiable gender-differences of striatal dopamine D2 receptor occupancy.

Clozapine as a Model for Antipsychotic Development

Schizophrenia is a devastating illness that affects up to 1% of the population; it is characterized by a combination of positive symptoms, negative symptoms, and cognitive impairment. Currently, treatment consists of one class of medications known as antipsychotics, which include typical (first-generation) and atypical (second-generation) agents. Unfortunately, antipsychotic medications have limited efficacy, with up to a third of patients lacking a full response. Clozapine, the first atypical antipsychotic developed, is the only medication shown to be superior to all other antipsychotics. However, owing to several life-threatening side effects and required enrollment in a registry with routine blood monitoring, clozapine is greatly underutilized in the US. Developing a medication as efficacious as clozapine with limited side effects would likely become the first-line therapy for schizophrenia and related disorders. In this review, we discuss the history of clozapine, landmark studies, and its clinical advantages and disadvantages. We further discuss the hypotheses for clozapine's superior efficacy based on neuroreceptor binding, and the limitations of a receptor-based approach to antipsychotic development. We highlight some of the advances from pharmacogenetic studies on clozapine and then focus on studies of clozapine using unbiased approaches such as pharmacogenomics and gene expression profiling. Finally, we examine how these approaches could provide insights into clozapine's mechanism of action and side-effect profile, and lead to novel and improved therapeutics.