Immunomodulatory effects of clozapine and their clinical implications: what have we learned so far?

Immune-based Machine learning Prediction of Diagnosis and Illness State in Schizophrenia and Bipolar Disorder

BACKGROUND

Schizophrenia and bipolar disorder frequently face significant delay in diagnosis, leading to being missed or misdiagnosed in early stages. Both disorders have also been associated with trait and state immune abnormalities. Recent machine learning-based studies have shown encouraging results using diagnostic biomarkers in predictive models, but few have focused on immune-based markers. Our main objective was to develop supervised machine learning models to predict diagnosis and illness state in schizophrenia and bipolar disorder using only a panel of peripheral kynurenine metabolites and cytokines.

METHODS

The cross-sectional I-GIVE cohort included hospitalized acute bipolar patients (n = 205), stable bipolar outpatients (n = 116), hospitalized acute schizophrenia patients (n = 111), stable schizophrenia outpatients (n = 75) and healthy controls (n = 185). Serum kynurenine metabolites, namely tryptophan (TRP), kynurenine (KYN), kynurenic acid (KA), quinaldic acid (QUINA), xanthurenic acid (XA), quinolinic acid (QUINO) and picolinic acid (PICO) were quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS), while V-plex Human Cytokine Assays were used to measure cytokines (interleukin-6 (IL-6), IL-8, IL-17, IL-12/IL23-P40, tumor necrosis factor-alpha (TNF-ɑ), interferon-gamma (IFN-γ)). Supervised machine learning models were performed using JMP Pro 17.0.0. We compared a primary analysis using nested cross-validation to a split set as sensitivity analysis. Post-hoc, we re-ran the models using only the significant features to obtain the key markers.

RESULTS

The models yielded a good Area Under the Curve (AUC) (0.804, Positive Prediction Value (PPV) = 86.95; Negative Prediction Value (NPV) = 54.61) for distinguishing all patients from controls. This implies that a positive test is highly accurate in identifying the patients, but a negative test is inconclusive. Both schizophrenia patients and bipolar patients could each be separated from controls with a good accuracy (SCZ AUC 0.824; BD AUC 0.802). Overall, increased levels of IL-6, TNF-ɑ and PICO and decreased levels of IFN-γ and QUINO were predictive for an individual being classified as a patient. Classification of acute versus stable patients reached a fair AUC of 0.713. The differentiation between schizophrenia and bipolar disorder yielded a poor AUC of 0.627.

CONCLUSIONS

This study highlights the potential of using immune-based measures to build predictive classification models in schizophrenia and bipolar disorder, with IL-6, TNF-ɑ, IFN-γ, QUINO and PICO as key candidates. While machine learning models successfully distinguished schizophrenia and bipolar disorder from controls, the challenges in differentiating schizophrenic from bipolar patients likely reflect shared immunological pathways by the both disorders and confounding by a larger state-specific effect. Larger multi-centric studies and multi-domain models are needed to enhance reliability and translation into clinic.

The effect of clozapine on immune-related biomarkers in schizophrenia patients

Globally, schizophrenia is one of the main causes of disability. Approximately 1 % of the general population suffers from schizophrenia, and 30 % of cases are unresponsive to therapy. Clozapine is the gold standard for therapy-resistant schizophrenia (TRS), yet it has limited effectiveness and serious adverse events in some patients. Because of the possibility of severe neutropenia, clozapine administration requires monthly hematological monitoring in the first four months. Previous investigations have demonstrated the immune system alteration after clozapine treatment in schizophrenia patients. Besides, it has been proposed that clozapine changes the cytokines profile in schizophrenia patients. These findings highlighted the need to learn more about the disease's etiology and investigate the relationship between peripheral immune system markers and clozapine response to support strategies for better treatment outcomes. The time decision-making to start clozapine could be significantly decreased if some biomarkers were developed to assist physicians in anticipating whether a particular patient will respond to the medication. Therefore, this study aimed to comprehensively review the effect of clozapine on immune-related biomarkers in schizophrenia patients.

Immunophenotyping schizophrenia subtypes stratified by antipsychotic response

Immune dysfunction has been proposed to play a role in the pathophysiology behind the development and persistence of psychosis. Current immunophenotyping studies are limited by small sample sizes and the number of immune markers investigated. Pharmacological subtypes in schizophrenia based on antipsychotic response have been proposed, but few studies have investigated immunophenotypes in treatment-resistant schizophrenia. In this study, we perform comprehensive immunophenotyping on 196 subjects comprising 147 schizophrenia patients stratified by antipsychotic response (49 antipsychotic-responsive, 70 clozapine-responsive, 28 clozapine-resistant) and 49 healthy controls. We aim to identify significant immune cell populations associated with schizophrenia and increasing treatment resistance, as potential modulators of underlying psychosis and/or treatment response. Patients with schizophrenia were recruited and assessed on the Clinical Global Impression - Schizophrenia (CGI-SCH). Treatment response was defined as a rating of three (mild severity) or less on the CGI-SCH positive symptom item after at least 8 weeks of adequate antipsychotic or clozapine treatment. Peripheral blood mononuclear cells were collected and flow cytometry was performed to identify 66 immune cell populations. Differences in cell population proportions were compared between schizophrenia cases and controls, and across all 4 groups, with post-hoc pairwise comparisons. Mucosal-associated invariant T (MAIT) cells (specifically CD8 + and DN double-negative subsets), total, exhausted and memory CD8 + T cells, VD1 + ϒδ T cells, plasmablasts, IgG + B cells and conventional dendritic cells 2 (cDC2) were among the top cell populations downregulated in schizophrenia. We observed increased downregulation with increasing treatment resistance. Conversely, naïve and exhausted CD4 + T cells, CD4/CD8 ratio and CCR5 + CCR2 + HLA DR + Myeloid cells were found to be upregulated in schizophrenia - we observed increased upregulation with increasing treatment resistance. We show significant immunophenotypic differences between schizophrenia cases and healthy controls, and consistent trend differences across varying degrees of antipsychotic resistance. We also examined immune cell populations not previously reported in schizophrenia. Future studies may explore immune markers identified as potential biomarkers of treatment resistance, and clarify on the relationship between immunological changes and pharmacological subtypes in schizophrenia.

When, Why and How to Re-challenge Clozapine in Schizophrenia Following Myocarditis

Clozapine-induced myocarditis (CIM) is among the most important adverse events limiting the use of clozapine as the most effective treatment for schizophrenia. CIM necessitates the immediate termination of clozapine, often resulting in its permanent discontinuation with considerable detrimental effects on patients' psychopathology and long-term outcome. Consequently, a clozapine re-challenge after CIM is increasingly regarded as a viable alternative, with published reports indicating a success rate of approximately 60%. However, published cases of re-challenges after CIM remain limited. Here, we provide a narrative review of the current state of research regarding the epidemiology, pathophysiology, risk factors, diagnosis and clinical management of CIM as well as a synthesis of current recommendations for re-challenging patients after CIM. This includes a step-by-step guide for this crucial procedure based on the current evidence regarding the pathophysiology and risk factors for CIM. Slow dose titration regimes and addressing risk factors including concomitant valproate and olanzapine are crucial both to prevent CIM and to ensure a safe and successful re-challenge. Furthermore, we discuss the utility of C-reactive protein, troponin, N-terminal-pro hormone and brain natriuretic peptide, therapeutic drug-monitoring and cardiac magnetic resonance imaging for CIM screening and diagnosis as well as for post-CIM re-challenges.

Immunoinflammatory features and cognitive function in treatment-resistant schizophrenia: unraveling distinct patterns in clozapine-resistant patients

Patients with treatment-resistant schizophrenia (TRS), particularly those resistant to clozapine (CTRS), pose a clinical challenge due to limited response to standard antipsychotic treatments. Inflammatory factors like tumor necrosis factor-alpha (TNF-α), interleukin 2 (IL-2), and interleukin 6 (IL-6) are implicated in schizophrenia's pathophysiology. Our study examines cognitive function, psychopathological symptoms and inflammatory factors in TRS patients, focusing on differences between CTRS and non-CTRS individuals, as well as healthy controls. A cohort of 115 TRS patients and 84 healthy controls were recruited, assessing IL-2, IL-6 and TNF-α. The Positive and Negative Syndrome Scale (PANSS) was applied to assess psychopathological symptoms, while the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) was applied to assess cognitive functioning. CTRS patients showed lower visuospatial constructional score (p = 0.015), higher PANSS scores, higher levels of IL-2 and reduced TNF-α than non-CTRS patients (p < 0.05). Notably, IL-2 was independently associated with psychopathology symptoms in CTRS patients (Beta = 0.268, t = 2.075, p = 0.042), while IL-6 was associated with psychopathology symptoms in non-CTRS patients (Beta = - 0.327, t = - 2.109, p = 0.042). Sex-specific analysis in CTRS patients revealed IL-2 associations with PANSS total and positive symptoms in females, and TNF-α associations with PANSS positive symptoms in males. Furthermore, IL-2, IL-6, and TNF-α displayed potential diagnostic value in TRS patients and CTRS patients (p < 0.05). Clozapine‑resistant symptoms represent an independent endophenotype in schizophrenia with distinctive immunoinflammatory characteristics, potentially influenced by sex.

Antipsychotic-Related DRESS Syndrome: Analysis of Individual Case Safety Reports of the WHO Pharmacovigilance Database

INTRODUCTION

Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is gaining attention in pharmacovigilance, but its association with antipsychotics, other than clozapine, is still unclear.

METHODS

We conducted a case/non-case study with disproportionality analysis based on the World Health Organization (WHO) global spontaneous reporting database, VigiBase®. We analyzed individual case safety reports of DRESS syndrome related to antipsychotics compared to (1) all other medications in VigiBase®, (2) carbamazepine (a known positive control), and (3) within classes (typical/atypical) of antipsychotics. We calculated reporting odds ratio (ROR) and Bayesian information component (IC), with 95% confidence intervals (CIs). Disproportionate reporting was prioritized based on clinical importance, according to predefined criteria. Additionally, we compared characteristics of patients reporting with serious/non-serious reactions.

RESULTS

A total of 1534 reports describing DRESS syndrome for 19 antipsychotics were identified. The ROR for antipsychotics as a class as compared to all other medications was 1.0 (95% CI 0.9-1.1). We found disproportionate reporting for clozapine (ROR 2.3, 95% CI 2.1-2.5; IC 1.2, 95% CI 1.1-1.3), cyamemazine (ROR 2.3, 95% CI 1.5-3.5; IC 1.2, 95% CI 0.5-1.7), and chlorpromazine (ROR 1.5, 95% CI 1.1-2.1; IC 0.6, 95% CI 0.1-1.0). We found 35.7% of cases with co-reported anticonvulsants, and 25% with multiple concurrent antipsychotics in serious compared to 8.6% in non-serious cases (p = 0.03). Fatal cases were 164 (10.7%).

CONCLUSIONS

Apart from the expected association with clozapine, chlorpromazine and cyamemazine (sharing an aromatic heteropolycyclic molecular structure) emerged with a higher-than-expected reporting of DRESS. Better knowledge of the antipsychotic-related DRESS syndrome should increase clinicians' awareness leading to safer prescribing of antipsychotics.

Overcoming clozapine's adverse events: a narrative review of systematic reviews and meta-analyses

INTRODUCTION

Clozapine is the gold standard treatment for treatment-resistant schizophrenia, however adverse events remain a clinical challenge.

AREAS COVERED

This review presents a narrative synthesis of systematic reviews and meta-analyses that have reported the onset, incidence, prevalence, and management of clozapine's adverse events. We conducted a systematic literature search using PubMed, Embase, PsycINFO, OvidMEDLINE, CINAHL, and the Cochrane Database of Systematic Reviews from inception to April 2024.

EXPERT OPINION

Effective management of clozapine's adverse events necessitates multi-faceted, individualized, and shared-decision strategies. Despite a lack of high-quality systematic evidence, expert inter-disciplinary solutions are provided to help address a critical need for clinical guidance. This 35-year update offers an evidence-based framework to assist clinicians, patients, and caregivers navigate the adverse events associated with clozapine therapy.

Blood Cell Count Ratios at Baseline are Associated with Initial Clinical Response to Clozapine in Treatment-Resistant, Clozapine-Naïve, Schizophrenia-Spectrum Disorder

BACKGROUND

Clozapine is the recommended treatment for managing treatment-resistant schizophrenia (TRS), and immunological mechanisms may be involved in its unique antipsychotic efficacy. This study investigated whether baseline immune abnormalities measured with blood cell count ratios can predict the clinical response after initiating treatment with clozapine in patients with clozapine naïve TRS.

METHODS

A longitudinal design was developed, involving 32 patients diagnosed with treatment-resistant, clozapine-naïve schizophrenia-spectrum disorder. Patients were evaluated at baseline before clozapine starting and 8 weeks of follow-up. Psychopathological status and immune abnormalities (blood cell count ratios: neutrophil-lymphocyte ratio [NLR], monocyte-lymphocyte ratio [MLR], platelet-lymphocyte ratio [PLR] and basophil-lymphocyte ratio [BLR]) were evaluated in each visit.

RESULTS

Baseline NLR (b=- 0.364; p=0.041) and MLR (b =- 0.400; p=0.023) predicted the change in positive symptoms over the 8-week period. Patients who exhibited a clinical response showed higher baseline NLR (2.38±0.96 vs. 1.75±0.83; p=0.040) and MLR (0.21±0.06 vs. 0.17±0.02; p=0.044) compared to non-responders. In the ROC analysis, the threshold points to distinguish between responders and non-responders were approximately 1.62 for NLR and 0.144 for MLR, yielding AUC values of 0.714 and 0.712, respectively. No statistically significant differences were observed in the blood cell count ratios from baseline to the 8-week follow-up.

CONCLUSION

Our study emphasizes the potential clinical significance of baseline NLR and MLR levels as predictors of initial clozapine treatment response in patients with TRS. Future studies with larger sample sizes and longer follow-up periods should replicate our findings.

Association between initial clozapine titration and pneumonia risk among patients with schizophrenia in a Korean tertiary hospital

Pneumonia is a significant adverse drug reaction (ADR) associated with clozapine, characterized by high mortality and potential linkage with other inflammatory responses. Despite the critical nature, research regarding the development of pneumonia during initial clozapine titration remains limited. This retrospective study included 1408 Korean inpatients with schizophrenia spectrum disorders. Data were collected from January 2000 to January 2023. Pneumonia developed in 3.5 % of patients within 8 weeks of clozapine initiation. Patients who developed pneumonia were taking a greater number and higher dose of antipsychotics at baseline (2.14 vs. 1.58, p < 0.001; 25.64 vs. 19.34, p = 0.012). The average onset occurred 17.24 days after initiation, on an average dose of 151.28 mg/day. Titration was either paused or slowed in most of these patients, with no reported fatalities. The types of pneumonia included aspiration pneumonia, mycoplasma pneumonia, bronchopneumonia, and COVID-19 pneumonia. Myocarditis, drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome, and urinary tract infections were also identified. Logistic regression analysis revealed that a greater number of concomitant antipsychotics (odds ratio [OR] = 1.59, p = 0.027) and concomitant benzodiazepine use (OR = 2.33, p = 0.005) at baseline were associated with an increased risk of pneumonia. Overall, pneumonia development during clozapine titration is linked with other inflammatory ADRs, suggesting a shared immunological mechanism. Close monitoring is recommended, especially for patients taking multiple antipsychotics and benzodiazepines. Further studies involving repeated measures of clozapine concentrations at trough and steady state, along with a more detailed description of pneumonia types, are warranted.

Eosinophils and Cognitive Impairment in Schizophrenia: A New Perspective

Schizophrenia is a complex psychiatric disorder characterized by a wide array of cognitive impairments. While research has predominantly focused on the neurological aspects of schizophrenia, emerging evidence suggests that the immune system, specifically eosinophils, may play a significant role in the cognitive deficits associated with the disorder. This review presents a novel perspective on the interplay between eosinophils and cognitive impairment in schizophrenia. Eosinophils, traditionally associated with allergic responses and inflammation, have garnered limited attention within the realm of neuropsychiatry. Recent studies have hinted at a potential link between eosinophil activation and the pathogenesis of schizophrenia. In this comprehensive review, we delve into the world of eosinophils, elucidating their nature, functions, and interactions with the immune system. We examine the cognitive deficits observed in individuals with schizophrenia and discuss existing theories on the etiology of these impairments, focusing on immune system involvement. The paper also highlights the evolving body of research that supports the idea of eosinophilic influence on schizophrenia-related cognitive deficits. Furthermore, we explore potential mechanisms through which eosinophils may exert their effects on cognitive function in schizophrenia, including interactions with other immune cells and inflammatory pathways. By discussing the clinical implications and potential therapeutic avenues stemming from this newfound perspective, we underscore the practical significance of this emerging field of research. While this paper acknowledges the limitations and challenges inherent in studying eosinophils within the context of schizophrenia, it serves as a posit for novel thought in this vexing disease space as well as a call to action for future research endeavors. By providing a comprehensive survey of the existing literature and posing unanswered questions, we aim to inspire a reimagining of the relationship between eosinophils and cognitive impairment in schizophrenia, ultimately advancing our understanding and treatment of this debilitating disorder.

Clozapine-induced cholinergic urticaria: a case report

Clozapine, renowned for its efficacy in treatment-resistant schizophrenia, is associated with rare yet potentially severe side effects, including hematological disorders, myocarditis, seizures and gastrointestinal obstruction. Dermatological adverse effects, though less serious, can profoundly impact patients' quality of life. We present the first reported case of cholinergic urticaria induced by clozapine, in a 25-year-old male with treatment-resistant schizophrenia. Four months into clozapine therapy, the patient developed intensely pruritic erythematous lesions triggered by sweating, significantly impairing his daily activities. Despite attempts at management, including dose reduction and antihistamine therapy, the urticaria persisted. However, a favorable outcome was achieved upon switching to quetiapine. This case underscores the importance of recognizing and managing treatment-related adverse effects, even when they arise late in treatment, and highlights the need for individualized therapeutic approaches.We discuss potential mechanisms underlying clozapine-induced cholinergic urticaria and emphasize the significance of patient-centered care in optimizing treatment outcomes in schizophrenia.

Change in absolute neutrophil count after COVID-19 infection in patients using clozapine versus other antipsychotics

It was reported that patients who contracted COVID-19 while taking clozapine exhibited a distinct hematological response. However, the absence of control groups made it difficult to attribute it to clozapine. The changes in absolute neutrophil counts (ANCs) during the 4 weeks after COVID-19 infection were compared between the two groups of patients with severe mental illnesses (SMIs) (49 patients using clozapine and 54 using other antipsychotics) using generalized additive modeling. Although the pattern of a transient drop in ANC followed by gradual recovery could be demonstrated in both groups, it was more pronounced in the clozapine group ( P  = 0.00025). Nevertheless, overall ANC remained at a higher level in the clozapine group. The results suggested potential interaction between clozapine and COVID-19 at the level of hematological dynamics. However, it did not necessarily indicate that such interaction is inevitably harmful or dangerous. It was more of a concern that some patients using other antipsychotics exhibited decreased ANC, which did not easily recover. Traditionally, clinicians have been concerned about the worsening of hematological side effects in clozapine patients after COVID-19 infection. However, the obtained result highlighted the necessity of hematological monitoring in patients using any type of antipsychotics for SMIs.

Changes in immunoglobulin levels during clozapine treatment in schizophrenia

BACKGROUND AND HYPOTHESIS

Use of clozapine in treatment-resistant schizophrenia is often limited due to risk of adverse effects. Cross-sectional associations between clozapine treatment and low immunoglobulin levels have been reported, however prospective studies are required to establish temporal relationships. We tested the hypothesis that reductions in immunoglobulin levels would occur over the first 6 months following initiation of clozapine treatment. Relationships between immunoglobulin levels and symptom severity over the course of clozapine treatment were also explored.

DESIGN

This prospective observational study measured immunoglobulin (Ig) levels (A, M and G) in 56 patients with treatment-resistant schizophrenia at 6-, 12- and 24-weeks following initiation with clozapine. Clinical symptoms were also measured at 12 weeks using the positive and negative syndrome scale (PANSS).

RESULTS

IgA, IgG and IgM all decreased during clozapine treatment. For IgA and IgG the reduction was significant at 24 weeks (IgA: β = -32.66, 95% CI = -62.38, -2.93, p = 0.03; IgG: β = -63.96, 95% CI = -118.00, -9.31, p = 0.02). For IgM the reduction was significant at 12 and 24 weeks (12 weeks: β = -23.48, 95% CI = -39.56, -7.42, p = 0.004; 24 weeks: β = -33.12, 95 %CI = -50.30, -15.94, p = <0.001). Reductions in IgA and IgG during clozapine treatment were correlated with reductions in PANSS-total over 12 weeks (n = 32, IgA r = 0.59, p = 0.005; IgG r = 0.48, p = 0.03).

CONCLUSIONS

The observed reductions in immunoglobulin levels over six months of clozapine treatment add further evidence linking clozapine to secondary antibody deficiency. Associations between Ig reduction and symptom improvement may however indicate that immune mechanisms contribute to both desirable and undesirable effects of clozapine.

Serum Interleukin-6 in Schizophrenia: Associations with Clinical and Sociodemographic Characteristics

BACKGROUND

Recently a significant part of schizophrenia studies have been focused on the role of cytokines, especially interleukin-6 (IL-6). Some authors have suggested a pathogenetic role for IL-6 in schizophrenia and concluded that therapy that centers on suppressing IL-6 activity may prove beneficial for certain categories of patients with the disorder. However, many questions about whether the changes in IL-6 levels in schizophrenia are primary, related to symptoms or caused by therapy, are concomitant metabolic disorders, are related to smoking or other secondary factors remain unanswered.

AIM

To assess the level of serum IL-6 in patients with schizophrenia in comparison with healthy controls, as well as to study its association with clinical and socio-demographic characteristics.

METHODS

Some 125 patients with schizophrenia and 95 healthy volunteers were examined. The evaluation of IL-6 was performed by enzyme immunoassay. All patients were assessed using standardized psychometric instruments. Information from patient medical records on the course of the disease and treatment was analyzed.

RESULTS

The level of IL-6 was significantly higher in the patients than in the healthy volunteers (z=2.58; p=0.0099), but among men the difference between the patients and volunteers was not significant. Statistically significant correlations were found between the level of serum IL-6 and the severity of the cognitive impairment of patients: (auditory [ρ=-0.31; p=0.00063] and working memory [ρ=-0.25; p=0.0065], hand-eye coordination [ρ=-0.29; p=0.0011], verbal fluency [ρ=-0.28; p=0.0019] and problem-solving capacity [ρ=-0.22; p=0.013]), total severity of schizophrenia symptoms (PANSS, ρ=0.22; p=0.016), PANSS positive subscale (ρ=0.18; p=0.048), and the age of manifestation (ρ=0.20; p=0.025) and disease duration (ρ=0.18; p=0.043). The level of IL-6 was the lowest in patients treated with third-generation antipsychotics, and the highest in those treated with first-generation antipsychotics (H=6.36; p=0.042). Moreover, in hospital patients, the level of IL-6 was significantly higher than in outpatients and inpatients hospitals (H=18.59; p=0.0001).

CONCLUSION

The study confirmed that there are associations between the serum IL-6 level and schizophrenia, the age of the patient, duration of the disease and how late in one's life cycle it began manifesting itself, as well as a number of clinical characteristics. Considering that IL-6 is associated with a wide range of symptoms that are loosely controlled by antipsychotics, this biochemical marker needs to be studied to look into how closely its level tracks with an unfavorable course of schizophrenia. That would require further prospective studies.

A systematic review of clozapine-associated inflammation and related monitoring

Clozapine is an effective antipsychotic medication used for treatment-resistant schizophrenia. However, it is underutilized due to rigorous hematologic monitoring requirements and many adverse drug reactions. Publications have highlighted the occurrence of inflammatory reactions, some life-threatening, particularly during the early stages of clozapine treatment. Although guidelines have suggested monitoring for inflammatory processes during clozapine initiation, screening in clinical practice is not universal. This systematic review aimed to investigate the relationship between clozapine and inflammation and assess the importance of monitoring for inflammatory reactions. A comprehensive literature search yielded 6915 unique publication records after removal of duplicates. After a rigorous screening process, 75 publications were included in the review, which focused on three main aspects: (i) the impact of clozapine on inflammatory markers, (ii) monitoring cardiac and other organ function during clozapine-associated inflammatory processes, and (iii) monitoring non-specific signs and symptoms of inflammation. Elevated levels of C-reactive protein (CRP) and several proinflammatory cytokines have been observed in association with clozapine treatment. However, the practicality of measuring specific markers in clinical practice remains uncertain. Current evidence supports monitoring CRP levels during the first 4-8 weeks of treatment, especially to facilitate myocarditis screening. Further research is needed to establish clinically relevant CRP thresholds for intervention. The implementation of monitoring protocols during the early phase of clozapine treatment may mitigate adverse reactions and allow for continued use of clozapine. Future studies should also explore the association between clozapine-associated inflammation and pneumonia, as well as investigate the impact of inflammation on clozapine metabolism to predict the need for dose adjustment. These endeavors may facilitate the development and implementation of evidence-based guidelines for the monitoring of clozapine-associated inflammation.

Inflammatory markers in outpatients with schizophrenia diagnosis in regular use of clozapine: a cross-sectional study

It is known that inflammation worsen the course of schizophrenia and induce high clozapine serum levels. However, no study evaluated this change in function of clozapine daily dose in schizophrenia. We assessed the correlation between inflammation and severity symptoms in patients with schizophrenia that take and do not take clozapine. We also assessed the correlation between clozapine daily dose and inflammatory markers to patients who take this drug. Patients were recruited from Schizophrenia Ambulatory and Psychosocial Care Center of Clinical Hospital of Porto Alegre and from an association of relatives of patients with schizophrenia. Exam results, and other important clinical exam were assessed in patients record or patients were asked to show their exam in the case of outpatients. We included 104 patients, 90 clozapine users and 14 non-clozapine users. We calculate the systemic inflammatory markers [neutrophil-lymphocyte ratio (NLR), systemic immune inflammation index (SII), and the psychopathology severity by the Brief Psychiatric Rating Scaled anchored (BPRS-a)]. These variables were compared between clozapine users and non-clozapine users. It was used mean/median test according to data distributing, with study factor (SII, MLR, and PLR), the clinical outcome: severity of symptomatology (BPRS score), and clozapine daily dose as adjustment factor. Clozapine users exhibited a significantly higher neutrophil count (mean ± SD: 5.03 ± 2.07) compared to non-clozapine users (mean ± SD: 3.48 ± 1.27; p = 0.031). After controlling for comorbidity, other parameters also showed significant differences. These findings are consistent with previous studies that have demonstrated an inflammatory response following the administration of clozapine.

Inflammatory markers in outpatients with schizophrenia diagnosis in regular use of clozapine: a cross-sectional study

It is known that inflammation worsen the course of schizophrenia and induce high clozapine serum levels. However, no study evaluated this change in function of clozapine daily dose in schizophrenia. We assessed the correlation between inflammation and severity symptoms in patients with schizophrenia that take and do not take clozapine. We also assessed the correlation between clozapine daily dose and inflammatory markers to patients who take this drug. Patients were recruited from Schizophrenia Ambulatory and Psychosocial Care Center of Clinical Hospital of Porto Alegre and from an association of relatives of patients with schizophrenia. Exam results, and other important clinical exam were assessed in patients record or patients were asked to show their exam in the case of outpatients. We included 104 patients, 90 clozapine users and 14 non-clozapine users. We calculate the systemic inflammatory markers [neutrophil-lymphocyte ratio (NLR), systemic immune inflammation index (SII), and the psychopathology severity by the Brief Psychiatric Rating Scaled anchored (BPRS-a)]. These variables were compared between clozapine users and non-clozapine users. It was used mean/median test according to data distributing, with study factor (SII, MLR, and PLR), the clinical outcome: severity of symptomatology (BPRS score), and clozapine daily dose as adjustment factor. Clozapine users exhibited a significantly higher neutrophil count (mean ± SD: 5.03 ± 2.07) compared to non-clozapine users (mean ± SD: 3.48 ± 1.27; p = 0.031). After controlling for comorbidity, other parameters also showed significant differences. These findings are consistent with previous studies that have demonstrated an inflammatory response following the administration of clozapine.

Infections associated with clozapine: a pharmacovigilance study using VigiBase®

Introduction: Clozapine is primarily reserved for treatment-resistant schizophrenia due to safety concerns associated with its use. Infections have been reported with clozapine, which may lead to elevated serum levels of the drug. However, the existing literature on this topic is limited. Therefore, we conducted a study using VigiBase® to investigate the potential over-reporting of infections associated with clozapine, to explore the presence of dose-dependency, and to investigate the underlying mechanism. Methods: Disproportionality analyses were performed using VigiBase to assess the association between clozapine and all types of infections, the association between clozapine-associated infections and neutropenia, the association between clozapine-associated infections and agranulocytosis, the dose-effect relationship between clozapine and infections, and the interaction between clozapine and the main strong CYP450 inhibitors using reports carried out until 11 April 2023. Results: A statistically significant signal of infections was observed with clozapine, as indicated by an information component of 0.43 [95% CI: (0.41-0.45)]. The most commonly reported infections were respiratory and gastrointestinal in nature. Neutropenia showed weaker association with clozapine-associated reports of infections compared to other clozapine-associated reports [X2 (1, N = 204,073) = 454; p < 0.005], while agranulocytosis demonstrated a stronger association with clozapine-associated reports of infections [X2 (1, N = 204,073) = 56; p < 0.005]. No evidence of dose-dependency was observed. Among the 17 tested CYP inhibitors, significant drug-drug interactions were found with clarithromycin, metronidazole, valproic acid, lansoprazole, omeprazole, amiodarone, and esomeprazole. Discussion: Our study revealed a significant safety signal between clozapine use and infections, predominantly respiratory and gastrointestinal infections. The co-administration of clozapine with valproic acid or proton pump inhibitors may potentially contribute to an increased risk of infection. Further vigilance is warranted in clinical practice, and consideration of therapeutic drug monitoring of clozapine in cases involving concomitant use of these drugs or in the presence of infections may be beneficial.

Early neutrophil trajectory following clozapine may predict clozapine response - Results from an observational study using electronic health records

BACKGROUND

Clozapine has unique effectiveness in treatment-resistant schizophrenia and is known to cause immunological side-effects. A transient spike in neutrophils commonly occurs in the first weeks of clozapine therapy. There is contradictory evidence in the literature as to whether neutrophil changes with clozapine are linked to treatment response.

AIMS

The current study aims to further examine the neutrophil changes in response to clozapine and explore any association between neutrophil trajectory and treatment response.

METHODS

A retrospective cohort study of patients undergoing their first treatment with clozapine and continuing for at least 2 years identified 425 patients (69% male/31% female). Neutrophil counts at baseline, 3 weeks and 1 month were obtained predominantly by linkage with data from the clozapine monitoring service. Clinical Global Impression- Severity (CGI-S) was rated from case notes at the time of clozapine initiation and at 2 years. Latent class growth analysis (LCGA) was performed to define distinct trajectories of neutrophil changes during the first month of treatment. Logistic regression was then conducted to investigate for association between the trajectory of neutrophil count changes in month 1 and clinical response at 2 years as well as between baseline neutrophil count and response.

RESULTS

Of the original cohort, 397 (93%) patients had useable neutrophil data during the first 6 weeks of clozapine treatment. LCGA revealed significant differences in neutrophil trajectories with a three-class model being the most parsimonious. The classes had similar trajectory profiles but differed primarily on overall neutrophil count: with low, high-normal and high neutrophil classes, comprising 52%, 40% and 8% of the sample respectively. Membership of the high-normal group was associated with significantly increased odds of a positive response to clozapine, as compared to the low neutrophil group [Odds ratio (OR) = 2.10, p-value = 0.002; 95% confidence interval (95% CI) = 1.31-3.36]. Baseline neutrophil count was a predictor of response to clozapine at 2 years, with counts of ≥5 × 109/l significantly associated with positive response (OR = 1.60, p-value = 0.03; 95% CI = 1.03-2.49).

CONCLUSIONS

Our data are consistent with the hypothesis that patients with low-level inflammation, reflected in a high-normal neutrophil count, are more likely to respond to clozapine, raising the possibility that clozapine exerts its superior efficacy via immune mechanisms.

Clozapine Optimization: A Delphi Consensus Guideline From the Treatment Response and Resistance in Psychosis Working Group

BACKGROUND AND HYPOTHESIS

There is limited evidence to guide the approaches to clozapine treatment. Accordingly, an international initiative was undertaken with the aim of developing consensus recommendations for the optimization of clozapine monotherapy.

STUDY DESIGN

We conducted an online Delphi survey among members of the Treatment Response and Resistance in Psychosis (TRRIP) working group comprising experts from twenty-nine countries. The threshold criterion for a consensus recommendation was ≥ 75% agreement ("agree" and "strongly agree" responses) on a question. Agreement of ≥ 50% but < 75% in a second or third Delphi round was deemed to provide guidance.

STUDY RESULTS

Forty-nine (first round), 32 (second round), and 48 (third round) of the 91 current TRRIP members participated. Expert recommendations at ≥ 75% comprised second-line treatment with clozapine in cases of persistent positive symptoms with co-occurring extrapyramidal symptoms, tardive dyskinesia, or suicidality/aggression. There was considerable disagreement on myocarditis screening parameters. The management of somatic and neuropsychiatric adverse drug reactions warrants further research for more evidence-based recommendations. Rechallenge with clozapine was recommended for eosinophilia, sinus tachycardia and fever and guidance (agreement ≥ 50%) was reached for pneumonia and thrombocytopenia.

CONCLUSIONS

Given the limited evidence available, this consensus-based series of recommendations and guidance statements supports clinical decision-making to optimize clozapine monotherapy and provides guidance for future research in treatment-resistant schizophrenia.

Alteration patterns of peripheral concentrations of cytokines and associated inflammatory proteins in acute and chronic stages of schizophrenia: a systematic review and network meta-analysis

BACKGROUND

Immune system dysfunction is considered to play an aetiological role in schizophrenia spectrum disorders, with substantial alterations in the concentrations of specific peripheral inflammatory proteins, such as cytokines. However, there are inconsistencies in the literature over which inflammatory proteins are altered throughout the course of illness. Through conducting a systematic review and network meta-analysis, this study aimed to investigate the patterns of alteration that peripheral inflammatory proteins undergo in both acute and chronic stages of schizophrenia spectrum disorders, relative to a healthy control population.

METHODS

In this systematic review and meta-analysis, we searched PubMed, PsycINFO, EMBASE, CINAHL, and the Cochrane Central Register of Controlled Trials from inception to March 31, 2022, for published studies reporting peripheral inflammatory protein concentrations in cases of people with schizophrenia-spectrum disorders and healthy controls. Inclusion criteria were: (1) observational or experimental design; (2) a population consisting of adults diagnosed with schizophrenia-spectrum disorders with a specified indicator of acute or chronic stage of illness; (3) a comparable healthy control population without mental illness; (4) a study outcome measuring the peripheral protein concentration of a cytokine, associated inflammatory marker, or C-reactive protein. We excluded studies that did not measure cytokine proteins or associated biomarkers in blood. Mean and SDs of inflammatory marker concentrations were extracted directly from full-text publshed articles; articles that did not report data as results or supplementary results were excluded (ie, authors were not contacted) and grey literature and unpublished studies were not sought. Pairwise and network meta-analyses were done to measure the standardised mean difference in peripheral protein concentrations between three groups: individuals with acute schizophrenia-spectrum disorder, individuals with chronic schizophrenia-spectrum disorder, and healthy controls. This protocol was registered on PROSPERO, CRD42022320305.

FINDINGS

Of 13 617 records identified in the database searches, 4492 duplicates were removed, 9125 were screened for eligibility, 8560 were excluded after title and abstract screening, and three were excluded due to limited access to the full-text article. 324 full-text articles were then excluded due to inappropriate outcomes, mixed or undefined schizophrenia cohorts, or duplicate study populations, five were removed due to concerns over data integrity, and 215 studies were included in the meta-analysis. 24 921 participants were included, with 13 952 adult cases of schizophrenia-spectrum disorder and 10 969 adult healthy controls (descriptive data for the entire cohort were not available for age, numbers of males and females, and ethnicity). Concentration of interleukin (IL)-1β, IL-1 receptor antagonist (IL-1RA), soluble interleukin-2 receptor (sIL-2R), IL-6, IL-8, IL-10, tumour necrosis factor (TNF)-α, and C-reactive protein were consistently elevated in both individuals with acute schizophrenia-spectrum disorder and chronic schizophrenia-spectrum disorder, relative to healthy controls. IL-2 and interferon (IFN)-γ were significantly elevated in acute schizophrenia-spectrum disorder, while IL-4, IL-12, and IFN-γ were significantly decreased in chronic schizophrenia-spectrum disorder. Sensitivity and meta-regression analyses revealed that study quality and a majority of the evaluated methodological, demographic, and diagnostic factors had no significant impact on the observed results for most of the inflammatory markers. Specific exceptions to this included: methodological factors of assay source (for IL-2 and IL-8), assay validity (for IL-1β), and study quality (for transforming growth factor-β1); demographic factors of age (for IFN-γ, IL-4, and IL-12), sex (for IFN-γ and IL-12), smoking (for IL-4), and BMI (for IL-4); and diagnostic factors including diagnostic composition of schizophrenia-spectrum cohort (for IL-1β IL-2, IL-6, and TNF-α), antipsychotic-free cases (for IL-4 and IL-1RA), illness duration (for IL-4), symptom severity (for IL-4), and subgroup composition (for IL-4).

INTERPRETATION

Results suggest that people with schizophrenia-spectrum disorders have a baseline level of inflammatory protein alteration throughout the illness, as reflected by consistently elevated pro-inflammatory proteins, hypothesised here as trait markers (eg, IL-6), while those with acute psychotic illness might have superimposed immune activity with increased concentrations of hypothesised state markers (eg, IFN-γ). Further research is required to determine whether these peripheral alterations are reflected within the central nervous system. This research facilitates an entry point in understanding how clinically relevant inflammatory biomarkers might one day be useful to the diagnosis and prognostication of schizophrenia-spectrum disorders.

FUNDING

None.

Reflections on the Lack of Consideration of Ethnic Ancestry to Stratify Clozapine Dosing

This review article argues against trusting standard clozapine references, including the US package insert, because they do not include advances in the sciences of pharmacokinetics and pharmacovigilance and ignore the effects of ethnic ancestry on therapeutic dosing. The minimum therapeutic dose leading to the minimum therapeutic concentration of 350 ng/mL in serum/plasma can be used to compare individuals/groups with treatment-resistant schizophrenia. The US clozapine package insert recommends targeting doses of 300-450 mg/day and, subsequently, increments of up to 100 mg with a maximum dose of 900 mg/day. Ethnic ancestry is defined by DNA ancestry group. Asians (people with ancestry ranging from Pakistan to Japan) and Indigenous Americans are similar in clozapine dosing; their average clozapine minimum therapeutic dose ranged from 166 mg/day (female non-smokers) to 270 mg/day (male smokers). For those with European ancestry, average clozapine minimum therapeutic doses ranged from 236 mg/day (female non-smokers) to 368 mg/day (male smokers). Based on limited studies, Black (African sub-Saharan ancestry) patients may be treated with typical US doses (300-600 mg/day), assuming no poor metabolism (PM) status. Ancestry's impact on clozapine lethality in four countries is discussed (two countries with highly homogenous populations, Denmark and Japan, and two countries with increasingly heterogenous populations due to immigration, Australia and the UK). An international guideline with 104 authors from 50 countries/regions was recently published, providing 6 personalized clozapine titration schedules for adult inpatients (3 ancestry groups and PM/non-PM schedules) and recommending c-reactive protein monitoring at baseline and weekly for 4 weeks.

COVID-19 Vaccines and the Virus: Impact on Drug Metabolism and Pharmacokinetics

This article reports on an American Society of Pharmacology and Therapeutics, Division of Drug Metabolism and Disposition symposium held at Experimental Biology on April 2, 2022, in Philadelphia. As of July 2022, over 500 million people have been infected with SARS-CoV-2 (the virus causing COVID-19) and over 12 billion vaccine doses have been administered. Clinically significant interactions between viral infections and hepatic drug metabolism were first recognized over 40 years ago during a cluster of pediatric theophylline toxicity cases attributed to reduced hepatic drug metabolism amid an influenza B outbreak. Today, a substantive body of research supports that the activated innate immune response generally decreases hepatic cytochrome P450 activity. The interactions extend to drug transporters and other organs and have the potential to impact drug absorption, distribution, metabolism, and excretion (ADME). Based on this knowledge, altered ADME is predicted with SARS-CoV-2 infection or vaccination. The report begins with a clinical case exploring the possibility of SARS-CoV-2 vaccination increasing clozapine levels. This is followed by discussions of how SARS-CoV-2 infection or vaccines alter the metabolism and disposition of complex drugs, such as nanoparticles and biologics and small molecule therapies. The review concludes with a discussion of the effects of viral infections on placental amino acid transport and their potential to impact fetal development. The session improved our understanding of the impact of emerging viral infections and vaccine technologies on drug metabolism and disposition, which will help mitigate drug toxicity and improve drug and vaccine safety and effectiveness. SIGNIFICANCE STATEMENT: Altered pharmacokinetics of small molecule and complex molecule drugs and fetal brain distribution of amino acids following SARS-CoV-2 infection or immunization are possible. The proposed mechanisms involve decreased liver cytochrome P450 metabolism of small molecules, enhanced innate immune system metabolism of complex molecules, and altered placental and fetal blood-brain barrier amino acid transport, respectively. Future research is needed to understand the effects of these interactions on adverse drug responses, drug and vaccine safety, and effectiveness and fetal neurodevelopment.

The Modernization of Clozapine: A Recapitulation of the Past in the United States and the View Forward

PURPOSE

Although clozapine was Food and Drug Administration (FDA) approved more than 3 decades ago, major barriers and gaps in knowledge continue to prevent its effective and safe use. We review modern-day problems encountered with clozapine in the United States (US).

METHODS

Information surrounding current administrative, clinical, research, and technological gaps or barriers related to clozapine use in the US was reviewed.

FINDINGS

The history of how clozapine became FDA approved likely contributes to gaps in knowledge. The frequency of safety warnings added to the FDA prescribing information may add to fears about clozapine, as evidence by numerous published survey studies. The clozapine Risk Evaluation and Mitigation Strategy (REMS) program has been modified several times in the last decade, causing access and safety issues for patients, which are discussed. Evidence may suggest that the FDA REMS requirements for hematologic monitoring are too cumbersome, and there may be ability to safely loosen requirements. The COVID-19 pandemic brought forth the ability for extended interval monitoring but also greater awareness of the clozapine-inflammation interaction. Newer guidelines published describe considerations in personalizing clozapine titration based on principles of ethnopsychopharmacology. Emerging technologies to support the use of clozapine are not widely available.

IMPLICATIONS

Clozapine is a unique life-saving drug but it is underused in the US, despite its established efficacy. The 2021 REMS changes led to significant difficulties for providers and patients. We highlight the importance of the clozapine-inflammation interaction, therapeutic drug monitoring, and the ability for individual care based on patient-specific factors. There is an urgent need for advancing technology used for clozapine monitoring, evaluating barriers created by REMS, and establishing consistent practices throughout the US.

Impact of clozapine on the expression of miR-675-3p in plasma exosomes derived from patients with schizophrenia

OBJECTIVES

Recently, the expression changes of microRNAs (miRNAs) in the serum exosomes (EXO) of schizophrenia (SCZ) have been reported. The aim of this study was to investigate the global expression changes of miRNA derived from the plasma EXO of patients with treatment-resistant schizophrenia (TRS) and the effects of clozapine on miRNA expression.

METHODS

Global miRNA expression changes in plasma EXO between TRS and controls were studied using microarray analysis. Then, miRNA expressions among TRS, non-TRS, and controls were confirmed with quantitative qPCR experiments. We also studied changes in EXO miRNA expression with in-vitro SH-SY5Y cells.

RESULTS

A microarray for miRNA expression analysis (nine controls vs. nine patients with TRS) revealed 13 up- and 18 downregulated miRNAs that were relevant to neuronal and brain development based on gene ontology analysis. Of those, upregulated miR-675-3p expression was successfully validated in the same cohort by qPCR experiments. Conversely, miR-675-3p expression levels were significantly decreased in the non-TRS cohort (50 controls vs. 50 patients without TRS without clozapine treatment).

CONCLUSIONS

We identified global miRNA changes in plasma EXO derived from patients with SCZ that were relevant to neuronal functions, among which, hsa-miR-675-3p expression was upregulated by clozapine treatment.

Recognition and management of clozapine adverse effects: A systematic review and qualitative synthesis

OBJECTIVE

Clozapine is substantially underutilized in most countries and clinician factors including lack of knowledge and concerns about adverse drug effects (ADEs) contribute strongly to treatment reluctance. The aim of this systematic review was to provide clinicians with a comprehensive information source regarding clozapine ADEs.

METHODS

PubMed and Embase databases were searched for English language reviews concerned with clozapine ADEs; publications identified by the automated search were manually searched for additional relevant citations. Following exclusion of redundant and irrelevant reports, pertinent information was summarized in evidence tables corresponding to each of six major ADE domains; two authors reviewed all citations for each ADE domain and summarized their content by consensus in the corresponding evidence table. This study was conducted in accordance with PRISMA principles.

RESULTS

Primary and secondary searches identified a total of 305 unique reports, of which 152 were included in the qualitative synthesis. Most clozapine ADEs emerge within 3 months, and almost all appear within 6 months, after initiation. Notable exceptions are weight gain, diabetic ketoacidosis (DKA), severe clozapine-induced gastrointestinal hypomotility (CIGH), clozapine-induced cardiomyopathy (CICM), seizures, and clozapine-induced neutropenia (CIN). Most clozapine ADEs subside gradually or respond to dose reduction; those that prompt discontinuation generally do not preclude rechallenge. Rechallenge is generally inadvisable for clozapine-induced myocarditis (CIM), CICM, and clozapine-induced agranulocytosis (CIA). Clozapine plasma levels >600-1000 μg/L appear more likely to cause certain ADEs (e.g., seizures) and, although there is no clear toxicity threshold, risk/benefit ratios are generally unfavorable above 1000 μg/L.

CONCLUSION

Clozapine ADEs rarely require discontinuation.

Distinctive pattern of neutrophil count change in clozapine-associated, life-threatening agranulocytosis

The wider use of clozapine is limited by the risk of agranulocytosis and the associated requirement for monitoring of neutrophil counts. We searched local electronic patient records for cases of agranulocytosis occurring during clozapine treatment during the period 2007–2020. We found 23 episodes recorded as agranulocytosis in clozapine patients. Of these, nine met pre-defined criteria and were considered episodes of life-threatening agranulocytosis (LTA). These episodes of clozapine-induced LTA exhibited a distinct pattern of continuous and rapid neutrophil count decline to zero or near zero. Mean time for neutrophils to fall from ANC > 2 to ANC <0.5 × 10⁹/L was 8.4 days (range 2–15 days). Each event was also characterised by a prolonged nadir and delayed recovery (range 4–16 days). Non-LTA episodes were, in contrast, brief and benign. We conclude that an important proportion of cases of agranulocytosis identified in people prescribed clozapine are not life-threatening and may not even be clozapine-related. Monitoring schemes should aim to identify true clozapine-induced LTA as opposed to threshold-defined nominal agranulocytosis. Genetics studies might benefit from examining associations with clozapine-induced LTA rather than with recorded cases of agranulocytosis or neutropenia.

Incident infection during the first year of treatment - A comparison of clozapine and paliperidone palmitate long-acting injection

BACKGROUND

To examine the risk of infection in patients prescribed clozapine compared with patients prescribed paliperidone palmitate long-acting injection (PPLAI).

METHOD

A retrospective, 1-year, cohort study conducted on events occurring in eligible patients beginning treatment for the first time with clozapine or PPLAI between June 2017 and June 2019 in a UK mental health trust providing in-patient and out-patient services.

RESULTS

The study included 64 patients starting clozapine and 120 patients starting PPLAI. Incidence of infection was greater in clozapine starters than in PPLAI starters (28% vs 6%; p = 0.001; adjusted odds ratio 5.82 (95% confidence interval (CI) = 2.15-15.76, p = 0.001). Infectious episodes in clozapine patients were not related to changes in neutrophil counts. Incident infection in the clozapine group was highest in the first 3 months of treatment. The most commonly reported infection in the clozapine group was chest infection; however, the majority of infections were non-chest-related.

CONCLUSION

Patients starting clozapine showed a substantially increased likelihood of infection compared with patients starting PPLAI.

Clozapine induces an acute proinflammatory response that is attenuated by inhibition of inflammasome signaling: implications for idiosyncratic drug-induced agranulocytosis

Although clozapine is a highly efficacious schizophrenia treatment, it is under-prescribed due to the risk of idiosyncratic drug-induced agranulocytosis (IDIAG). Clinical data indicate that most patients starting clozapine experience a transient immune response early in treatment and a similar response has been observed in clozapine-treated rats, but the mechanism by which clozapine triggers this transient inflammation remains unclear. Therefore, the aim of this study was to characterize the role of inflammasome activation during the early immune response to clozapine using in vitro and in vivo models. In both differentiated and nondifferentiated human monocytic THP-1 cells, clozapine, but not its structural analogues fluperlapine and olanzapine, caused inflammasome-dependent caspase-1 activation and IL-1β release that was inhibited using the caspase-1 inhibitor yVAD-cmk. In Sprague Dawley rats, a single dose of clozapine caused an increase in circulating neutrophils and a decrease in lymphocytes within hours of drug administration along with transient spikes in the proinflammatory mediators IL-1β, CXCL1, and TNF-α in the blood, spleen, and bone marrow. Blockade of inflammasome signaling using the caspase-1 inhibitor VX-765 or the IL-1 receptor antagonist anakinra attenuated this inflammatory response. These data indicate that caspase-1-dependent IL-1β production is fundamental for the induction of the early immune response to clozapine and, furthermore, support the general hypothesis that inflammasome activation is a common mechanism by which drugs associated with the risk of idiosyncratic reactions trigger early immune system activation. Ultimately, inhibition of inflammasome signaling may reduce the risk of IDIAG, enabling safer, more frequent use of clozapine in patients.

How an increase in the copy number of HSV-1 during latency can cause Alzheimer's disease: the viral and cellular dynamics according to the microcompetition model

Numerous studies observed a link between the herpes smplex virus-1 (HSV-1) and Alzheimer's disease. However, the exact viral and cellular dynamics that lead from an HSV-1 infection to Alzheimer's disease are unknown. In this paper, we use the microcompetition model to formulate these dynamics by connecting seemingly unconnected observations reported in the literature. We concentrate on four pathologies characteristic of Alzheimer's disease. First, we explain how an increase in the copy number of HSV-1 during latency can decrease the expression of BECN1/Beclin1, the degradative trafficking protein, which, in turn, can cause a dysregulation of autophagy and Alzheimer's disease. Second, we show how an increase in the copy number of the latent HSV-1 can decrease the expression of many genes important for mitochondrial genome metabolism, respiratory chain, and homeostasis, which can lead to oxidative stress and neuronal damage, resulting in Alzheimer's disease. Third, we describe how an increase in this copy number can reduce the concentration of the NMDA receptor subunits NR1 and NR2b (Grin1 and Grin2b genes), and brain derived neurotrophic factor (BDNF), which can cause an impaired synaptic plasticity, Aβ accumulation and eventually Alzheimer's disease. Finally, we show how an increase in the copy number of HSV-1 in neural stem/progenitor cells in the hippocampus during the latent phase can lead to an abnormal quantity and quality of neurogenesis, and the clinical presentation of Alzheimer's disease. Since the current understanding of the dynamics and homeostasis of the HSV-1 reservoir during latency is limited, the proposed model represents only a first step towards a complete understanding of the relationship between the copy number of HSV-1 during latency and Alzheimer's disease.

Clozapine Response in Schizophrenia and Hematological Changes

BACKGROUND

Clozapine is the only effective medication for treatment-resistant schizophrenia; however, its mechanism of action remains unclear. The present study explored whether its effectiveness is related to changes in hematological measures after clozapine initiation.

METHODS

Patients with treatment-resistant schizophrenia commenced on clozapine between January 2007 and December 2014 by the United Kingdom's largest mental health trust were identified from electronic patient records. Hematological data from these patients were obtained from a monitoring registry. White blood cell, neutrophil, and platelet count were assessed at baseline and during the early phase of clozapine treatment. Clozapine response at 3 months was defined as "much," or "very much" improved on the seven-point Clinical Global Impression-Improvement (CGI-I) subscale.

RESULTS

In the total sample (n = 188), clozapine initiation was associated with a significant transient increase (peaking in weeks 3 to 4) in white blood cell, neutrophil, and platelet count (P < 0.001). There were 112 (59.6%) patients that responded to treatment; however, none of the hematological factors assessed at baseline, nor changes in these factors, were directly associated with treatment response.

IMPLICATIONS

Clozapine treatment is associated with transient hematological changes during the first month of treatment; however, there was no evidence that these were related to the therapeutic response.

Unravelling cases of clozapine-related Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) in patients reported otherwise: A systematic review

BACKGROUND

The drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is a drug-induced hypersensitivity reaction.

AIMS

Aim was to review reports of clozapine-related reactions fulfilling the registry of severe cutaneous adverse reaction (RegiSCAR) criteria for DRESS syndrome reported as such or otherwise, to provide a descriptive overview of demographic patterns, clinical manifestations, and DRESS course and investigate associations between demographic, DRESS parameters, and clinical outcomes.

METHODS

This review was conducted following preferred reporting items for systematic reviews and meta-analyses guidelines and registered with PROSPERO (registration number CRD42020156385). We searched PubMed/Embase/PsychInfo/Cochrane for reports of clozapine-related reactions meeting RegiSCAR criteria. Associations between RegiSCAR scores and time-to-recovery with demographic/clinical variables were assessed. Demographic/clinical characteristics of patients with versus without reported DRESS were compared using non-parametrical tests.

RESULTS

We identified 26 reports of 27 patients meeting RegiSCAR criteria. Males (n = 19, 70.4%) and patients with schizophrenia (n = 18, 66.7%) were mainly affected. Twelve patients (44.4%) received clozapine-monotherapy. DRESS symptoms manifested within a month after clozapine initiation (n = 24, 88.9%). Lungs and liver were the most common organs involved (n = 12, 44.4%; n = 11, 40.7%), with a mean time to recovery of 33.75 days. Clozapine rechallenge led to DRESS recurrence in four patients. Death rate was 7.4%. No associations were detected between RegiSCAR criteria or days to recovery with any demographic/clinical variables. No differences between patients with versus without reported DRESS were detected.

CONCLUSIONS

Clozapine-related DRESS may be rare, but also underreported. Clinicians need to be aware of it even in patients under clozapine-monotherapy or without skin rash.

Challenges in Prescribing Clozapine in the Era of COVID-19: A Review Focused on Immunological Implications

The global COVID-19 pandemic has disrupted every aspect of the healthcare system. Apart from the issues surrounding COVID-19 itself, care for existing patients has met many challenges. One such challenge is caring for patients who are on clozapine treatment and have been confirmed positive for COVID-19. Schizophrenia has been considered to have a deep connection with the immune system, and clozapine can induce further changes in this system. COVID-19 can ravage the compromised immune system and aggravate tissue damage. The intricate relations between schizophrenia, clozapine, and COVID-19 make it difficult to predict the clinical course of COVID-19 in clozapine-treated patients. However, the rigid prohibition on using clozapine if COVID-19 is confirmed may harm patients. Patients who have to use clozapine are often refractory cases with no alternatives. Therefore, the decision to maintain or stop clozapine must be made after a comprehensive review of the patient’s unique situation. To do this, theoretical and practical issues surrounding the use of clozapine in COVID-19 should be reviewed and discussed. In this review, we gather useful information surrounding this issue and present an overview. Focusing on the immune system, various theoretical possibilities that could arise from schizophrenia, clozapine, and COVID-19 were carefully examined, and practical checklists for the care of these patients were explored. It is hoped that this review will convince many clinicians to pay attention to this momentous issue and facilitate more active sharing of clinical experiences.

Leukocytosis Associated with Clozapine Treatment: A Case Series and Systematic Review of the Literature

BACKGROUND AND OBJECTIVES

Clozapine is the only antipsychotic approved for treatment-resistant schizophrenia. Despite its superior efficacy profile as compared with other antipsychotics, clozapine remains underutilized. Clozapine monitoring systems clearly describe the proposed management of clozapine-induced neutropenia; however, no specific mention is made of how to interpret neutrophilic leukocytosis, despite that being a relatively frequent finding. Prescribers unfamiliar with this molecule may misjudge its clinical significance, potentially leading to untimely treatment interruption. Here, we systematically review the literature on the risk of neutrophilic leukocytosis during clozapine treatment, and describe eight additional cases among our patient cohort.

MATERIALS AND METHODS

We performed a systematic review of the literature on PubMed and Embase using the PRISMA 2020 guidelines, and selected all original reports describing either (1) the prevalence of neutrophilic leukocytosis during clozapine treatment, or (2) the clinical significance of neutrophilic leukocytosis. We described eight additional cases of neutrophilic leukocytosis during clozapine treatment while attending an outpatient psychiatric clinic.

RESULTS

Our research ultimately yielded the selection of 13 articles included in this systematic review. The case series highlighted the presence of stable and clinically unremarkable neutrophilia during a follow-up ranging from one to ten years.

CONCLUSIONS

Existing evidence indicates that leukocytosis associated with clozapine treatment can be considered as an asymptomatic and benign condition, suggesting that no change in clozapine treatment is needed upon its detection.

Clozapine: Why Is It So Uniquely Effective in the Treatment of a Range of Neuropsychiatric Disorders?

Clozapine is superior to other antipsychotics as a therapy for treatment-resistant schizophrenia and schizoaffective disorder with increased risk of suicidal behavior. This drug has also been used in the off-label treatment of bipolar disorder, major depressive disorder (MDD), and Parkinson's disease (PD). Although usually reserved for severe and treatment-refractory cases, it is interesting that electroconvulsive therapy (ECT) has also been used in the treatment of these psychiatric disorders, suggesting some common or related mechanisms. A literature review on the applications of clozapine and electroconvulsive therapy (ECT) to the disorders mentioned above was undertaken, and this narrative review was prepared. Although both treatments have multiple actions, evidence to date suggests that the ability to elicit epileptiform activity and alter EEG activity, to increase neuroplasticity and elevate brain levels of neurotrophic factors, to affect imbalances in the relationship between glutamate and γ-aminobutyric acid (GABA), and to reduce inflammation through effects on neuron-glia interactions are common underlying mechanisms of these two treatments. This evidence may explain why clozapine is effective in a range of neuropsychiatric disorders. Future increased investigations into epigenetic and connectomic changes produced by clozapine and ECT should provide valuable information about these two treatments and the disorders they are used to treat.

Associations Between Genotype and Peripheral Complement Proteins in First-Episode Psychosis: Evidences From C3 and C4

Schizophrenia is a common neuropsychiatric disorder with complex pathophysiology. Recent reports suggested that complement system alterations contributed to pathological synapse elimination that was associated with psychiatric symptoms in schizophrenia. Complement component 3 (C3) and complement component 4 (C4) play central roles in complement cascades. In this study, we compared peripheral C3 and C4 protein levels between first-episode psychosis (FEP) and healthy control (HC). Then we explored whether single nucleotide polymorphisms (SNPs) at C3 or C4 genes affect peripheral C3 or C4 protein levels. In total, 181 FEPs and 204 HCs were recruited after providing written informed consent. We measured serum C3 and C4 protein levels using turbidimetric inhibition immunoassay and genotyped C3 and C4 polymorphisms using the Sequenom MassArray genotyping. Our results showed that three SNPs were nominally associated with schizophrenia (rs11569562/C3: A > G, p = 0.048; rs2277983/C3: A > G, p = 0.040; rs149898426/C4: G > A, p = 0.012); one haplotype was nominally associated with schizophrenia, constructed by rs11569562–rs2277983–rs1389623 (GGG, p = 0.048); FEP had higher serum C3 and C4 (both p < 0.001) levels than HC; rs1389623 polymorphisms were associated with elevated C3 levels in our meta-analysis (standard mean difference, 0.50; 95% confidence interval, 0.30 to 0.71); the FEP with CG genotype of rs149898426 had higher C4 levels than that with GG genotypes (p = 0.005). Overall, these findings indicated that complement system altered in FEP and rs149898426 of C4 gene represented a genetic risk marker for schizophrenia likely through mediating complement system. Further studies with larger sample sizes needs to be validated.

The Emerging Role of the Innate Immune Response in Idiosyncratic Drug Reactions

Idiosyncratic drug reactions (IDRs) range from relatively common, mild reactions to rarer, potentially life-threatening adverse effects that pose significant risks to both human health and successful drug discovery. Most frequently, IDRs target the liver, skin, and blood or bone marrow. Clinical data indicate that most IDRs are mediated by an adaptive immune response against drug-modified proteins, formed when chemically reactive species of a drug bind to self-proteins, making them appear foreign to the immune system. Although much emphasis has been placed on characterizing the clinical presentation of IDRs and noting implicated drugs, limited research has focused on the mechanisms preceding the manifestations of these severe responses. Therefore, we propose that to address the knowledge gap between drug administration and onset of a severe IDR, more research is required to understand IDR-initiating mechanisms; namely, the role of the innate immune response. In this review, we outline the immune processes involved from neoantigen formation to the result of the formation of the immunologic synapse and suggest that this framework be applied to IDR research. Using four drugs associated with severe IDRs as examples (amoxicillin, amodiaquine, clozapine, and nevirapine), we also summarize clinical and animal model data that are supportive of an early innate immune response. Finally, we discuss how understanding the early steps in innate immune activation in the development of an adaptive IDR will be fundamental in risk assessment during drug development. SIGNIFICANCE STATEMENT: Although there is some understanding that certain adaptive immune mechanisms are involved in the development of idiosyncratic drug reactions, the early phase of these immune responses remains largely uncharacterized. The presented framework refocuses the investigation of IDR pathogenesis from severe clinical manifestations to the initiating innate immune mechanisms that, in contrast, may be quite mild or clinically silent. A comprehensive understanding of these early influences on IDR onset is crucial for accurate risk prediction, IDR prevention, and therapeutic intervention.

Clozapine, neutropenia and Covid-19: should clinicians be concerned? 3 months report

BACKGROUND

Clozapine is among the most effective antipsychotics used for treatment resistant schizophrenia. Adverse reactions to clozapine include neutropenia. In March 2020, at the start of the Coronavirus -19 pandemic, clinicians raised concerns regarding continuation of antipsychotic treatment, and specifically of clozapine, in patients with coronavirus disease. We aimed here at providing a short report focusing on the association between neutropenia and clozapine in a case series of psychiatric inpatients diagnosed with COVID-19.

PATIENTS & METHODS

We retrospectively inspected data of 10 patients on clozapine, admitted to Highgate Mental Health Centre, Camden & Islington NHS Foundation Trust, between March and July 2020; selection was based on their COVID-19 positive PCR test. We used a linear regression model to estimate whether there was a significant drop in the neutrophil count during SARS-CoV-2 infection.The analysis was done in R using a linear regression to the origin.

RESULTS

Data were collected on 10 patients, of which 7 were males. During COVID-19 infection, neutrophils' count (ANC) was 4.13 ​× ​109/l (SD ​= ​2.70) which constituted a significant drop from a baseline value of 5.2 ​× ​109/l (SD ​= ​2.24). The mean relative reduction in ANC was -0.2729 (SD ​= ​0.1666). The beta value of 0.8377 obtained with the linear regression showed that ANC values during SARS-CoV-2 infection were 83.77% of the baseline ANC showing that within the two time points there was a decrease of 16.23%. The linear regression had a pvalue ​= ​8.96 ​× ​10-8 and an adjusted R2 of 95.94% which shows that the variability of the data is very well explained by the model. We also compared baseline ANC with ANC values approximately a month after resolution of the infection and results indicate that ANC values return to a 95% of baseline.

CONCLUSIONS

Clinicians should bear in mind that a significant drop in neutrophils' count may occur in patients taking clozapine and affected from a SARS-CoV-2 infectionand that this drop is only transitory.

Suspected Recurrence of Symptomatic COVID-19: Management During Inpatient Psychiatric Treatment

The widespread prevalence of coronavirus disease 2019 (COVID-19) means that inpatient psychiatric units will necessarily manage patients who have COVID-19 that is comorbid with acute psychiatric symptoms. We report a case of recurrence of respiratory symptoms and positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reverse transcription-polymerase chain reaction (RT-PCR) testing in a patient on an inpatient psychiatric unit occurring 42 days after the initial positive SARS-CoV-2 RT-PCR test, 38 days after initial symptom resolution, and 30 days after the first of 3 negative SARS-CoV-2 RT-PCR tests. Over the course of the admission, the patient was safely initiated on clozapine. Recent literature on COVID-19's potential recurrence and neuropsychiatric effects is reviewed and implications for the management of COVID-19 on inpatient psychiatric units are discussed. In the era of COVID-19 and our still-developing understanding of this illness, psychiatrists' role as advocates and collaborators in our patients' physical health care has become even more critical.

The neuropsychiatric manifestations of COVID-19: Interactions with psychiatric illness and pharmacological treatment

The recent outbreak of the corona virus disease (COVID-19) has had major global impact. The relationship between severe acute respiratory syndrome coronavirus (SARS-CoV-2) infection and psychiatric diseases is of great concern, with an evident link between corona virus infections and various central and peripheral nervous system manifestations. Unmitigated neuro-inflammation has been noted to underlie not only the severe respiratory complications of the disease but is also present in a range of neuro-psychiatric illnesses. Several neurological and psychiatric disorders are characterized by immune-inflammatory states, while treatments for these disorders have distinct anti-inflammatory properties and effects. With inflammation being a common contributing factor in SARS-CoV-2, as well as psychiatric disorders, treatment of either condition may affect disease progression of the other or alter response to pharmacological treatment. In this review, we elucidate how viral infections could affect pre-existing psychiatric conditions and how pharmacological treatments of these conditions may affect overall progress and outcome in the treatment of SARS-CoV-2. We address whether any treatment-induced benefits and potential adverse effects may ultimately affect the overall treatment approach, considering the underlying dysregulated neuro-inflammatory processes and potential drug interactions. Finally, we suggest adjunctive treatment options for SARS-CoV-2-associated neuro-psychiatric symptoms.

Clozapine re-challenge and initiation following neutropenia: a review and case series of 14 patients in a high-secure forensic hospital

OBJECTIVE

Clozapine remains the most effective intervention for treatment resistant schizophrenia; however, its use is prohibited following neutropenias. We review neutrophil biology as applied to clozapine and describe the strategies to initiate clozapine following neutropenia used in a case series of 14 consecutive patients rechallenged in a United Kingdom (UK) high-secure psychiatric hospital. We examine outcomes including the use of seclusion and transfer.

METHODS

A case series of 14 male patients with treatment resistant schizophrenia treated with clozapine despite previous episodes of neutropenia between 2006 and 2015 is presented. Data were collected during 2015 and 2019. Using this routinely collected clinical data, we describe the patient characteristics, causes of neutropenia, the strategies used for rechallenging with clozapine and clinical outcomes.

RESULTS

Previous neutropenias were the result of benign ethnic neutropenia, clozapine, other medications and autoimmune-related. Our risk mitigation strategies included: granulocyte-colony stimulating factor (G-CSF), lithium and watch-and-wait. There were no serious adverse events; at follow up half of the patient's had improved sufficiently to transfer them to conditions of lesser security. There were dramatic reductions in the use of seclusion.

CONCLUSION

Even in this extreme group, clozapine can be safely and effectively re/initiated following neutropenias, resulting in marked benefits for patients. This requires careful planning based on an understanding of neutrophil biology and the aetiology of the specific episode of neutropenia.

Do proinflammatory cytokines play a role in clozapine-associated glycometabolism disorders?

RATIONALE AND OBJECTIVE

Clozapine (CLZ) is the most effective drug for treatment-resistant schizophrenia but is associated with many side effects, including glycometabolism disorders. Immunological mechanisms may be involved in the development of clozapine side effects. Research relating the immunomodulatory effects of clozapine and its early markers to clinically relevant adverse events is needed to reduce the harmful side effects of clozapine. This study aimed to investigate the role of proinflammatory cytokines in clozapine-associated glycometabolism disorders.

METHODS

We measured the effect of a range of doses of clozapine on glycometabolism-related parameters and proinflammatory cytokines levels in mice peripheral blood. We also examined the differences between these indicators in the peripheral blood of clozapine-treated schizophrenia patients and healthy controls. Furthermore, we detected proinflammatory cytokines expression in mice pancreatic tissue.

RESULTS

Following clozapine administration, glucagon significantly decreased in mouse serum, and proinflammatory cytokine IL-β levels markedly increased. Clozapine reliably increased proinflammatory cytokines (IL-1β, IL-6, and TNF-α) expression in murine pancreatic tissue. Compared with healthy controls, clozapine-treated patients' BMI, blood glucose, and proinflammatory cytokines (IL-1β, IL-6, and TNF-α) increased significantly. In clozapine-treated patients, a higher clozapine daily dosage was associated with higher levels of the proinflammatory cytokines IL-1β and IL-6, and a significant positive correlation was observed between blood glucose levels and the proinflammatory cytokines IL-6 and TNF-α.

CONCLUSION

Findings from animal experiments and clinical trials have shown clear evidence that clozapine has a regulatory effect on immune-related proinflammatory cytokines and influences glycometabolism indicators.

Safety of Psychotropic Medications in People With COVID-19: Evidence Review and Practical Recommendations

(Reprinted with permission from the BMC Medicine (2020) 18:215).

Clinical and laboratory characteristics of clozapine-treated patients with schizophrenia referred to a national immunodeficiency clinic reveals a B-cell signature resembling common variable immunodeficiency (CVID)

AIMS

An association between antibody deficiency and clozapine use in individuals with schizophrenia has recently been reported. We hypothesised that if clozapine-associated hypogammaglobulinaemia was clinically relevant this would manifest in referral patterns.

METHODS

Retrospective case note review of patients referred and assessed by Immunology Centre for Wales (ICW) between January 2005 and July 2018 with extraction of clinical and immunological features for individuals with diagnosis of schizophrenia-like illness.

RESULTS

1791 adult patients were assessed at ICW during this period; 23 patients had a psychiatric diagnosis of schizophrenia or schizoaffective disorder. Principal indications for referral were findings of low calculated globulin and immunoglobulins. Clozapine was the single most commonly prescribed antipsychotic (17/23), disproportionately increased relative to reported use in the general schizophrenia population (OR 6.48, 95% CI: 1.79 to 23.5). Clozapine therapy was noted in 6/7 (86%) of patients subsequently requiring immunoglobulin replacement therapy (IgRT). Marked reduction of class-switched memory B cells (CSMB) and plasmablasts were observed in clozapine-treated individuals relative to healthy age-matched controls. Clozapine duration is associated with CSMB decline. One patient discontinued clozapine, with gradual recovery of IgG levels without use of IgRT.

CONCLUSIONS

Our findings are consistent with enrichment of clozapine-treatment within schizophrenic individuals referred for ICW assessment over the last 13 years. These individuals displayed clinical patterns closely resembling the primary immunodeficiency common variable immunodeficiency, however appears reversible on drug cessation. This has diagnostic, monitoring and treatment implications for psychiatry and immunology teams and directs prospective studies to address causality and the wider implications for this patient group.

Schizophrenia and Epigenetic Aging Biomarkers: Increased Mortality, Reduced Cancer Risk, and Unique Clozapine Effects

BACKGROUND

Schizophrenia (SZ) is associated with increased all-cause mortality, smoking, and age-associated proteins, yet multiple previous studies found no association between SZ and biological age using Horvath's epigenetic clock, a well-established aging biomarker based on DNA methylation. However, numerous epigenetic clocks that may capture distinct aspects of aging have been developed. This study tested the hypothesis that altered aging in SZ manifests in these other clocks.

METHODS

We performed a comprehensive analysis of 14 epigenetic clocks categorized according to what they were trained to predict: chronological age, mortality, mitotic divisions, or telomere length. To understand the etiology of biological age differences, we also examined DNA methylation predictors of smoking, alcohol, body mass index, serum proteins, and cell proportions. We independently analyzed 3 publicly available multiethnic DNA methylation data sets from whole blood, a total of 567 SZ cases and 594 nonpsychiatric controls.

RESULTS

All data sets showed accelerations in SZ for the 3 mortality clocks up to 5 years, driven by smoking and elevated levels of 6 age-associated proteins. The 2 mitotic clocks were decelerated in SZ related to antitumor natural killer and CD8T cells, which may help explain conflicting reports about low cancer rates in epidemiological studies of SZ. One cohort with available medication data showed that clozapine is associated with male-specific decelerations up to 7 years in multiple chronological age clocks.

CONCLUSIONS

Our study demonstrates the utility of studying the various epigenetic clocks in tandem and highlights potential mechanisms by which mental illness influences long-term outcomes, including cancer and early mortality.