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)

Immune response to vaccination in people with psychotic disorders relative to healthy controls: prospective study of SARS-CoV-2 vaccination

This prospective study examines the immune response to SARS-CoV-2 vaccination in patients with psychotic disorders compared with healthy volunteers. Participants were recruited naturalistically as part of the UK's COVID-19 vaccination programme. Prior to receiving their first COVID-19 vaccine, blood samples were provided by participants to examine anti-SARS-CoV-2 immunoglobulins (IgG) at baseline, followed by a repeat assay 1 month after receiving their first vaccine to assess vaccine response. The increase of IgG levels from baseline to 1 month post-vaccination was significantly lower in patients compared with controls, supporting evidence of impaired vaccine response in people with psychotic disorders. When excluding patients treated with clozapine from the analysis, this difference was no longer significant, suggesting that effects may be particularly marked in people taking clozapine.

Vaccination and clozapine use: a systematic review and an analysis of the VAERS database

In the context of COVID-19 concerns related to the potential interactions between clozapine and vaccination arose. With the ultimate goal of deriving recommendations for clinical practice, we systematically reviewed the current evidence regarding altered vaccine effectiveness in clozapine-treated patients and safety aspects of vaccination, such as haematological changes and the impact of vaccines on clozapine blood levels, in clozapine-treated patients. A systematic PRISMA-conform literature search of four databases (PubMed, PsycINFO, EMBASE and Cochrane Library) complemented by a case-by-case analysis of the Vaccine Adverse Event Reporting System (VAERS) database was performed. We then systematically appraised the joint evidence and tried to derive recommendations for clinical practice. 14 records were included in this analysis. These records consisted of 5 original articles and 9 case reports. Among the original articles, two studies provided data on the association between clozapine use and antibody responses to vaccination, both indicating that clozapine use in schizophrenia may be associated with reduced levels of immunoglobulins. Additionally, three studies examined vaccine safety in clozapine-treated patients, with no clinically significant adverse effects directly attributable to the interplay between vaccinations and clozapine. VAERS Analysis encompassed 137 reports and showed no consistent evidence of an increased risk for clozapine blood level increases or adverse events. We found no evidence indicating that clozapine impairs the effectiveness of vaccines. Moreover, no serious safety concerns seem to apply when patients on clozapine are receiving vaccines. However, it is crucial to acknowledge that data on the interaction between clozapine and vaccines remain limited.

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.

Mediation and longitudinal analysis to interpret the association between clozapine pharmacokinetics, pharmacogenomics, and absolute neutrophil count

Clozapine is effective at reducing symptoms of treatment-resistant schizophrenia, but it can also induce several adverse outcomes including neutropenia and agranulocytosis. We used linear mixed-effect models and structural equation modelling to determine whether pharmacokinetic and genetic variables influence absolute neutrophil count in a longitudinal UK-based sample of clozapine users not currently experiencing neutropenia (N = 811). Increased daily clozapine dose was associated with elevated neutrophil count, amounting to a 133 cells/mm3 rise per standard deviation increase in clozapine dose. One-third of the total effect of clozapine dose was mediated by plasma clozapine and norclozapine levels, which themselves demonstrated opposing, independent associations with absolute neutrophil count. Finally, CYP1A2 pharmacogenomic activity score was associated with absolute neutrophil count, supporting lower neutrophil levels in CYP1A2 poor metabolisers during clozapine use. This information may facilitate identifying at-risk patients and then introducing preventative interventions or individualised pharmacovigilance procedures to help mitigate these adverse haematological reactions.

[Management of hypogammaglobulinemia]

Hypogammaglobulinemia (hypoγ) is defined as a serum IgG level < 7 g/L. It is most often detected on serum protein electrophoresis. Given the existence of transient hypoγ, its persistence should be checked at distance, preferably by requesting a blood test for IgG, IgA and IgM, which will be needed to characterize a possible primary immune deficiency (PID). In the case of association with a monoclonal component, the first step is to look for a cryoglobulin causing a false hypoγ. Otherwise, the etiological investigation is dictated by the clinical examination. For example, the notion of chronic diarrhea should lead to a search for an enteropathy causing a digestive loss of gammaglobulins (an ambiguous situation because some DIP can be complicated by an enteropathy). In the absence of an obvious explanation, a secondary cause must first be ruled out (secondary immune deficiencies are 30 times more common than PID). The first simple test to perform is 24-hour proteinuria, coupled with urinary protein electrophoresis, to rule out 2 diagnoses: nephrotic syndrome and light chain myeloma. Subsequently, blood immunophenotyping looking for a circulating B clone is recommended, allowing the investigations to be directed towards a lymphoid hemopathy. Drug-induced hypoγ may also be suspected if certain drugs such as corticosteroids, anti-epileptics or immunosuppressive agents (especially anti-CD20) are taken. The profile of a drug-induced hypoγ is different from that of a DIP: it is rarely profound, the IgA level is preserved and there is no deficit in switched memory B lymphocytes. Finally, a thoracoabdominal CT-scan will help to rule out a thymoma and identify a deep tumor syndrome. If all these tests are normal, a PID is suspected, the leader of which in adults remains the common variable immunodeficiency, which is the most frequent symptomatic PID in adults.

Rituximab as an adjunctive treatment for schizophrenia spectrum disorder or obsessive-compulsive disorder: Two open-label pilot studies on treatment-resistant patients

In this explorative study, we investigated if an adjunctive treatment with one single dose of the monoclonal antibody rituximab would improve symptoms and function in treatment-resistant patients with schizophrenia spectrum disorder (SSD, n = 9) or obsessive-compulsive disorder (OCD, n = 10), based on the inflammatory hypothesis for mental disorders. Patients were followed for one year. Disability was measured with the Personal and Social Performance score (PSP). At baseline, the mean PANSS score in the SSD group was 99 ± 32 and the mean Y-BOCS score in the OCD group was 27.5 ± 7. Mean PSP scores were 32 ± 10.2 and 42.5 ± 9.9 in the SSD and OCD groups, respectively. Seven had Paediatric Acute-Onset Neuropsychiatric Syndrome (PANS) in retrospect, and 3 SSD patients had schizo-obsessive subtype. 4/8 SSD patients showed a ≥40% reduction in PANSS at endpoint I week 20, however, 7/9 were similarly improved already at week 12. Among the OCD patients, 2/10 showed a ≥35% reduction in Y-BOCS at week 20. Disability was significantly improved only in the SSD group. The percentual decrease of PANSS scores in SSD patients was associated with the increase in immunoglobulin levels week 20 (n = 8: IgG r = 0.85, p = .007; IgA r = 0.79, p = .019; IgM r = 0.73, p = .038). Rituximab was generally well tolerated in these patients. Self-rated improvements since baseline were reported for psychic (p = .021), neurological (p = .059), and autonomic (p < .001) side effects (UKU-SERS-Pat side-effect scale). Anxiety was commonly reported by OCD patients, while an initial increase in psychotic symptoms was seen in a few SSD patients. An RCT is underway to evaluate rituximab in SSD.

Practical guidance for the diagnosis and management of secondary hypogammaglobulinemia: A Work Group Report of the AAAAI Primary Immunodeficiency and Altered Immune Response Committees

Secondary hypogammaglobulinemia (SHG) is characterized by reduced immunoglobulin levels due to acquired causes of decreased antibody production or increased antibody loss. Clarification regarding whether the hypogammaglobulinemia is secondary or primary is important because this has implications for evaluation and management. Prior receipt of immunosuppressive medications and/or presence of conditions associated with SHG development, including protein loss syndromes, are histories that raise suspicion for SHG. In patients with these histories, a thorough investigation of potential etiologies of SHG reviewed in this report is needed to devise an effective treatment plan focused on removal of iatrogenic causes (eg, discontinuation of an offending drug) or treatment of the underlying condition (eg, management of nephrotic syndrome). When iatrogenic causes cannot be removed or underlying conditions cannot be reversed, therapeutic options are not clearly delineated but include heightened monitoring for clinical infections, supportive antimicrobials, and in some cases, immunoglobulin replacement therapy. This report serves to summarize the existing literature regarding immunosuppressive medications and populations (autoimmune, neurologic, hematologic/oncologic, pulmonary, posttransplant, protein-losing) associated with SHG and highlights key areas for future investigation.

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.

Reasons for admission to a general medical hospital for patients taking clozapine

BACKGROUND

Clozapine is associated with a diverse range of side effects. In addition, patients prescribed clozapine commonly suffer with medical comorbidities.

OBJECTIVES

This study aimed to characterise patients prescribed clozapine who required medical admission, understand reasons for admission, identify areas for interventions to prevent future admission and describe clozapine management during the inpatient stay.

DESIGN

We conducted a retrospective analysis of patients prescribed clozapine who were admitted to a general medical hospital in a 12-month period.

METHOD

Data were collected using electronic drug charts and notes.

RESULTS

In total, 114 clozapine patients were hospitalised. Twenty-eight patients (25%) were admitted because of infection, 12 (11%) were elective admissions and 12 (11%) had gastrointestinal problems. Most patients admitted were Black (54%) and half were female. Few changes were made to clozapine dosing on admission or during the inpatient stay. Most patients had been taking clozapine for many years at the point of admission, the majority were able to continue taking it for the duration of their medical treatment and were discharged on the same dose they were taking prior to admission. Clozapine plasma concentrations were not consistently measured with only 18 (16%) patients having one or more plasma concentrations determined during their admission. The median clozapine plasma concentration on admission was 0.48 mg/L (nor-clozapine 0.21 mg/L), with a range of 0.09 to 3.9 mg/L. Three patients were admitted to the intensive care unit during their admission; all were discharged on clozapine. Four patients died; one from lung adenocarcinoma, one bowel obstruction, one cardiac arrest and one chest sepsis. In total, 27 patients (23%) had their clozapine stopped on admission, 6 (22% of this group) unintentionally.

CONCLUSIONS

Our study found that the most common reason for admission for patients taking clozapine was infection. Plasma concentrations were not measured routinely despite clozapine having a narrow therapeutic index and enhanced potential for toxicity in the medically unwell patient.

Clozapine treatment and risk of severe COVID-19 infection

OBJECTIVE

To investigate whether patients with clozapine treatment are at an increased risk of a more severe COVID-19 infection as compared with patients on other antipsychotic drugs.

METHODS

In this register-based cohort study, all residents (age 18 or older) in the Stockholm Region with a psychotic disorder diagnosis and antipsychotic treatment were included (N = 8 233) and followed from 1 March 2020 to 14 January 2021. The exposure was defined as clozapine treatment and the outcome measures (indicating a more severe COVID-19 infection) were: inpatient care, care within intensive care unit or death due to COVID-19 infection. Differences in outcome rates between exposed (n = 966) and unexposed (other antipsychotics; n = 7 267) were examined using Cox proportional hazards models and expressed as hazard ratios (HR) with 95% confidence intervals (CI).

RESULTS

No statistically significant differences in outcome rates were found between the two groups of patients after adjusting for age, sex and residence in retirement homes. The adjusted HR for the exposed compared to the unexposed was 0.96 (95% CI: 0.54, 1.70) for inpatient care; 1.69 (0.48, 5.93) for care in intensive care unit (ICU); and 0.86 (0.26, 2.80) for death. Regarding inpatient care, additional adjusting for country of birth, living in socioeconomically vulnerable areas, number of care visits during the previous year, and comorbid medical illnesses did not alter the results.

CONCLUSIONS

Our results may add support to the present guidelines, recommending sustained clozapine treatment during the current COVID-19 pandemic with careful monitoring and readiness to alter drug doses as needed.

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.

Exploring a Safety Signal of Antipsychotic-Associated Pneumonia: A Pharmacovigilance-Pharmacodynamic Study

An association between antipsychotic drugs and pneumonia has been demonstrated in several studies; however, the risk for pneumonia caused by specific antipsychotics has not been extensively studied. The underlying mechanism is still unknown, and several receptor mechanisms have been proposed. Therefore, using a combined pharmacovigilance-pharmacodynamic approach, we aimed to investigate safety signals of US Food and Drug Administration (FDA)-approved antipsychotics for reporting pneumonia and the potential receptor mechanisms involved. A disproportionality analysis was performed to detect a signal for reporting "infective-pneumonia" and "pneumonia-aspiration" and antipsychotics using reports submitted between 2004 and 2019 to the FDA adverse events spontaneous reporting system (FAERS) database. Disproportionality was estimated using the crude and the adjusted reporting odds ratio (aROR) and its 95% confidence interval (CI) in a multivariable logistic regression. Linear regressions investigated the relationship between aROR and receptor occupancy, which was estimated using in vitro receptor-binding profiles. Safety signals for reporting infective-pneumonia were identified for clozapine (LL = 95% 3.4, n = 546 [aROR: 4.8]) as well as olanzapine (LL = 95% 1.5, n = 250 [aROR: 2.1]) compared with haloperidol, while aRORs were associated with higher occupancies of muscarinic receptors (beta = .125, P-value = .016), yet other anti-muscarinic drugs were not included as potential confounders. No safety signals for reporting pneumonia-aspiration were detected for individual antipsychotics. Multiple antipsychotic use was associated with both reporting infective-pneumonia (LL 95%: 1.1, n = 369 [aROR:1.2]) and pneumonia-aspiration (LL 95%: 1.7, n = 194 [aROR: 2.0]). Considering the limitations of disproportionality analysis, further pharmacovigilance data and clinical causality assessment are needed to validate this safety signal.

COVID-19 infection causes a reduction in neutrophil counts in patients taking clozapine

BACKGROUND

Monitoring of white cell counts during clozapine treatment leads to cessation of therapy if levels fall below predetermined values. Reductions in white cell counts, driven by lower levels of lymphocytes, have been observed with coronavirus disease 2019 (COVID-19). Neutropenia during COVID-19 has not been reported. We present data for 56 patients who were taking clozapine and had COVID-19.

METHODS

We included patients who were taking clozapine at the time they tested positive for COVID-19. We compared absolute neutrophil counts, lymphocyte counts and white cell counts between baseline and the first week of infection, and baseline and the second week of infection.

RESULTS

We observed reductions in absolute neutrophil counts (p = 0.005), lymphocyte counts (p = 0.003) and white cell counts (p < 0.001) between baseline and the first 7 days of COVID-19. All cell counts had returned to baseline levels by days 8 to 14. Six patients experienced neutropenia (absolute neutrophil counts < 2.0 × 109/L) and of those, 4 underwent mandatory cessation of clozapine. For 3 patients, clozapine treatment had been established for more than 6 months with no previous neutropenia, neutrophil levels returned to baseline within 2 weeks and no further neutropenia was observed on restarting treatment.

LIMITATIONS

This was a retrospective chart review; larger cohorts are required. Clozapine plasma levels were largely not measured by clinicians.

CONCLUSION

These data strongly suggest that mild neutropenia in the acute phase of COVID-19 in patients who are well established on clozapine is more likely to be a consequence of the virus than of clozapine treatment.

Use of Clozapine in the General Hospital

Patients with treatment-resistant schizophrenia receiving clozapine therapy are at risk of potentially serious complications in the general hospital setting, due to the complex pharmacokinetic and pharmacodynamic profile of clozapine. We summarize common clinical challenges that face clinicians who care for clozapine patients in the general hospital, and make recommendations based on the available literature and clinical experience. Early collaborative management between consultation-liaison psychiatry and other clinical teams in the general hospital is paramount to improve clinical outcomes and avoid serious complications in this patient group.

The role of sulpiride in attenuating the cardiac, renal, and immune disruptions in rats receiving clozapine: mRNA expression pattern of the genes encoding Kim-1, TIMP-1, and CYP isoforms

The present study was aimed to explore the cardio-, immuno-, and nephrotoxic effects of the antipsychotic agent clozapine (CLZ) and the alleviative potency of sulpiride (SPD) on these impairments in rats. For this purpose, 40 male rats were divided into four groups and were orally treated with saline (control), CLZ (0.5 mg/kg bw), SPD (28 mg/kg bw), or a combination of CLZ and SPD (CLZ+SPD), daily for 30 consecutive days. At necropsy, blood samples and specimens from the heart, kidneys, and spleen were collected for biochemical, molecular, and histopathological investigations. The results showed that CLZ administration was associated with significantly lower immune status indices and increased serum levels of pro-inflammatory cytokines, lactate dehydrogenase, malondialdehyde, cardiac, and renal tissues injury markers. Moreover, the mRNA expression levels of Kidney Injury Molecule-1 (Kim-1), tissue inhibitor of metalloproteinase-1 (TIMP-1), and cytochrome P450 (CYP) isoforms were markedly upregulated in CLZ-treated rats, compared to the control group. On the other hand, rats treated with SPD alone showed non-significant differences in terms of immune response indices, tissue injury markers, and mRNA expression levels of Kim-1, TIMP-1, and CYP isoforms. Finally, CLZ+SPD co-treatment significantly modulated almost all biochemical indices. Besides, Kim-1, TIMP-1, and CYP2C19 mRNA expression levels were significantly downregulated, while other CYP isoforms showed no modulation, compared with CLZ-treated group. Histopathologically, CLZ-treated rats showed severe lesions in renal, splenic, and cardiac tissues, compared with control rats, which were restored in CLZ+SPD-co-treated rats. Overall, these findings demonstrate that CLZ treatment induces significant cardiac, immune, and nephropathic alterations, which were reduced with CLZ+SPD co-treatment.

Management of clozapine treatment during the COVID-19 pandemic

Clozapine is the only available treatment for refractory schizophrenia but its use involves frequent physical contact with healthcare workers for the purpose of mandatory blood monitoring. During the COVID-19 pandemic, patients taking clozapine will be self-isolating to reduce the risk of infection, not least because these patients are at high risk of serious illness and fatality because of high rates of diabetes, obesity and pulmonary disease and an increased risk of pneumonia. Problems may also arise because both clozapine-induced myocarditis and neutropenic sepsis share signs and symptoms with COVID-19 (fever, chest pain, dyspnoea, etc.). We recommend decreasing the frequency of physical contacts by extending the blood monitoring interval to 12 weeks in those patients taking clozapine for more than 1 year. To distinguish COVID-19 from clozapine-related physical adverse effects, we suggest an urgent antigen test alongside a full blood count. In those taking clozapine who develop COVID-19, we suggest continuing with clozapine whenever possible (even during ventilation), reducing the dose if necessary in line with blood assay results. Blood monitoring should continue but clozapine should only cease if there is a significant fall in neutrophils (COVID-19 is linked to lymphopenia but not neutropenia). To protect against the likelihood and severity of respiratory infection, we recommend the use of vitamin D in all clozapine patients. Initiation of clozapine is likely to remain problematic while the risk of infection remains, given the degree of physical contact required to assure safety.

Clozapine prescribing in COVID-19 positive medical inpatients: a case series

There is both uncertainty regarding the safety of clozapine in COVID-19 patients owing to limited published data and a lack of consensus on continuing clozapine in patients with severe respiratory infections. COVID-19 is known to induce an acute immune response which can affect haematological parameters associated with clozapine monitoring, and systemic infection may reduce clozapine clearance. Clozapine, which has been associated with worse outcomes in some pneumonias, may in theory worsen outcomes in COVID-19. Despite these concerns, there are some data to indicate it is safe to continue clozapine in COVID-19 infection. In this retrospective case series, we describe our experiences of clozapine prescribing and disease progression of eight SARS-CoV-2 positive patients on medical wards in a major London teaching hospital. In four cases clozapine was stopped during the hospital admission. A COVID-19 pneumonia developed in four patients: three of these required intensive care unit admission for an average of 34 days. At the time of writing, three patients had died (two directly from COVID-19 pneumonia), two remained in general hospital wards, two were recovering in the community and one had been transferred to an inpatient psychiatric hospital. Follow-up length varied but in each case was not more than 104 days. Delirium was the most common adverse neuropsychiatric event, and in one case a relapse of psychosis occurred after cessation of clozapine. This retrospective case series illustrates the safe use of clozapine during COVID-19 infection. Our experiences suggest that consideration should be made to continuing clozapine even in those most unwell with COVID-19. We also identify areas which require larger scale hypothesis-testing research.