Identification and characterization of thiamine analogs with antiplasmodial activity.

Thiamine is metabolized into thiamine pyrophosphate (TPP), an essential enzyme cofactor. Previous work has shown that oxythiamine, a thiamine analog, is metabolized by thiamine pyrophosphokinase (TPK) into oxythiamine pyrophosphate within the malaria parasite Plasmodium falciparum and then inhibits TPP-dependent enzymes, killing the parasite in vitro and in vivo. To identify a more potent antiplasmodial thiamine analog, 11 commercially available compounds were tested against P. falciparum and P. knowlesi. Five active compounds were identified, but only N3-pyridyl thiamine (N3PT), a potent transketolase inhibitor and candidate anticancer lead compound, was found to suppress P. falciparum proliferation with an IC50 value 10-fold lower than that of oxythiamine. N3PT was active against P. knowlesi and was >17 times less toxic to human fibroblasts, as compared to oxythiamine. Increasing the extracellular thiamine concentration reduced the antiplasmodial activity of N3PT, consistent with N3PT competing with thiamine/TPP. A transgenic P. falciparum line overexpressing TPK was found to be hypersensitized to N3PT. Docking studies showed an almost identical binding mode in TPK between thiamine and N3PT. Furthermore, we show that [3H]thiamine accumulation, resulting from a combination of transport and metabolism, in isolated parasites is reduced by N3PT. Treatment of P. berghei-infected mice with 200 mg/kg/day N3PT reduced their parasitemia, prolonged their time to malaria symptoms, and appeared to be non-toxic to mice. Collectively, our studies are consistent with N3PT competing with thiamine for TPK binding and inhibiting parasite proliferation by reducing TPP production, and/or being converted into a TPP antimetabolite that inhibits TPP-dependent enzymes.

Benralizumab for allergic asthma: a randomised, double-blind, placebo-controlled trial.

BACKGROUND: Benralizumab induces rapid and near-complete depletion of eosinophils from blood and lung tissue. We investigated whether benralizumab could attenuate the allergen-induced late asthmatic response (LAR) in participants with allergic asthma. METHODS: Participants with allergic asthma who demonstrated increased sputum eosinophils and LAR at screening were randomised to benralizumab 30 mg or matched placebo given every 4 weeks for 8 weeks (3 doses). Allergen challenges were performed at weeks 9 and 12 when blood, sputum, bone marrow and bronchial tissue eosinophils and LAR were assessed. RESULTS: 46 participants (mean age 30.9 years) were randomised to benralizumab (n=23) or placebo (n=23). Eosinophils were significantly reduced in the benralizumab group compared with placebo in blood at 4 weeks and sputum and bone marrow at 9 weeks after treatment initiation. At 7 h after an allergen challenge at week 9, sputum eosinophilia was significantly attenuated in the benralizumab group compared to placebo (least squares mean difference -5.81%, 95% CI -10.69- -0.94%; p=0.021); however, the LAR was not significantly different (least squares mean difference 2.54%, 95% CI 3.05-8.12%; p=0.363). Adverse events were reported for seven (30.4%) and 14 (60.9%) participants in the benralizumab and placebo groups, respectively. CONCLUSION: Benralizumab administration over 8 weeks resulted in a significant attenuation of blood, bone marrow and sputum eosinophilia in participants with mild allergic asthma; however, there was no change in the LAR, suggesting that eosinophils alone are not a key component of allergen-induced bronchoconstriction.

Thiamine analogues featuring amino-oxetanes as potent and selective inhibitors of pyruvate dehydrogenase.

Pyruvate dehydrogenase complex (PDHc) is suppressed in some cancer types but overexpressed in others. To understand its contrasting oncogenic roles, there is a need for selective PDHc inhibitors. Its E1-subunit (PDH E1) is a thiamine pyrophosphate (TPP)-dependent enzyme and catalyses the first and rate-limiting step of the complex. In a recent study, we reported a series of ester-based thiamine analogues as selective TPP-competitive PDH E1 inhibitors with low nanomolar affinity. However, when the ester linker was replaced with an amide for stability reasons, the binding affinity was significantly reduced. In this study, we show that an amino-oxetane bioisostere of the amide improves the affinity and maintains stability towards esterase-catalysed hydrolysis.

Autoantibody-mediated Macrophage Dysfunction in Patients with Severe Asthma with Airway Infections.

Rationale: Localized autoimmune responses have been reported in patients with severe eosinophilic asthma, characterized by eosinophil degranulation and airway infections. Objective: To determine the presence of autoantibodies against macrophage scavenger receptors within the airways and their effects on macrophage function and susceptibility to infection. Methods: Anti-EPX (eosinophil peroxidase), anti-MARCO (macrophage receptor with collagenous structure) IgG titers, and T1 and T2 (type 1/2) cytokines were measured in 221 sputa from 143 well-characterized patients with severe asthma. Peripheral monocytes and MDMs (monocyte-derived macrophages) isolated from healthy control subjects were treated with immunoprecipitated immunoglobulins from sputa with high anti-MARCO titers or nonspecific IgG to assess uptake of Streptococcus pneumoniae or response to the bacterial product LPS. Measurements and Main Results: Anti-MARCO IgG was detected in 36% of patients, with significantly higher titers (up to 1:16) in patients with mixed granulocytic sputa, indicative of airway infections. Multivariate regression analysis confirmed increased frequency of degranulation (free eosinophil granules), increased blood eosinophils (indicative of high T2 burden), increased sputum total cell count, peripheral blood leukocytes (indicative of infection), and lymphopenia were associated with increased anti-MARCO IgG titers; IL-15 (odds ratio [OR], 1.79; confidence interval [CI], 1.19-2.70), IL-13 (OR, 1.06; CI, 1.02-1.12), and IL-12p70 (OR, 3.34; CI, 1.32-8.40) were the associated cytokines. Patients with anti-MARCO antibodies had higher chances of subsequent infective versus eosinophilic exacerbations (P = 0.01). MDMs treated with immunoprecipitated immunoglobulins (anti-MARCO+ sputa) had reduced bacterial uptake by 39% ± 15% and significantly reduced release of IL-10 and granulocyte-macrophage colony-stimulating factor (GM-CSF) (P < 0.05) in response to an LPS stimulus. Conclusions: Autoantibodies against macrophage scavenger receptors in eosinophilic asthma airways may impede effective host defenses and lead to recurrent infective bronchitis.

Anti-epithelial-derived cytokines for severe asthma: Systematic review and meta-analysis.

BACKGROUND: Therapies directed against epithelial-derived cytokines, often referred to as alarmins, have been studied in large randomized trials, and reports suggest possible benefit for non-type 2 as well as type 2 severe asthma. METHODS: We performed a systematic review of Medline, Embase, Cochrane Central Register of Controlled Trials, Medline In-Process, and Web of Science databases from inception to March 2022. We performed a random-effects pairwise meta-analysis of randomized controlled trials addressing antialarmin therapy in severe asthma. Results use relative risk (RR) values and 95% confidence intervals (CIs). For continuous outcomes, we report mean difference (MD) values and 95% CIs. We define high eosinophils as ≥300 cells/µL and low eosinophils as <300 cells/µL. We used Cochrane-endorsed RoB 2.0 software to assess the risk of bias of trials, and we used the Grades of Recommendation Assessment, Development, and Evaluation (aka GRADE) framework to assess the certainty of the evidence. RESULTS: We identified 12 randomized trials including 2391 patients. Antialarmins probably reduce annualized exacerbation rates in patients with high eosinophils (RR 0.33 [95% CI 0.28 to 0.38]; moderate certainty). Antialarmins may reduce this rate in patients with low eosinophils (RR 0.59 [95% CI 0.38 to 0.90]; low certainty). Antialarmins improve FEV1 in patients with high eosinophils (MD 218.5 mL [95% CI 160.2 to 276.7]; high certainty). Antialarmin therapy probably does not improve FEV1 in patients with low eosinophils (MD 68.8 mL [95% CI 22.4 to 115.2]; moderate certainty). Antialarmins reduce blood eosinophils, total IgE, and fractional excretion of nitric oxide across studied subjects. CONCLUSION: Antialarmins are effective at improving lung function and probably reduce exacerbations in patients with severe asthma and blood eosinophils ≥300 cells/µL. The effect on patients with lower eosinophils is less certain.

Immune Response Dynamics and Biomarkers in COVID-19 Patients.

BACKGROUND: The immune response dynamics in COVID-19 patients remain a subject of intense investigation due to their implications for disease severity and treatment outcomes. We examined changes in leukocyte levels, eosinophil activity, and cytokine profiles in patients hospitalized with COVID-19. METHODS: Serum samples were collected within the first 10 days of hospitalization/confirmed infection and analyzed for eosinophil granule proteins (EGP) and cytokines. Information from medical records including comorbidities, clinical symptoms, medications, and complete blood counts were collected at the time of admission, during hospitalization and at follow up approximately 3 months later. RESULTS: Serum levels of eotaxin, type 1 and type 2 cytokines, and alarmin cytokines were elevated in COVID-19 patients, highlighting the heightened immune response (p < 0.05). However, COVID-19 patients exhibited lower levels of eosinophils and eosinophil degranulation products compared to hospitalized controls (p < 0.05). Leukocyte counts increased consistently from admission to follow-up, indicative of recovery. CONCLUSION: Attenuated eosinophil activity alongside elevated chemokine and cytokine levels during active infection, highlights the complex interplay of immune mediators in the pathogenesis COVID-19 and underscores the need for further investigation into immune biomarkers and treatment strategies.

Examining the effect of the COVID-19 pandemic on community virus prevalence and healthcare utilisation reveals that peaks in asthma, COPD and respiratory tract infection occur with the re-emergence of rhino/enterovirus.

INTRODUCTION: Airway disease exacerbations are cyclical related to respiratory virus prevalence. The COVID-19 pandemic has been associated with reduced exacerbations possibly related to public health measures and their impact on non-COVID-19 respiratory viruses. We aimed to investigate the prevalence of non-COVID-19 respiratory viruses during the pandemic compared with prior in Ontario, Canada and healthcare utilisation related to asthma, chronic obstructive pulmonary disease (COPD) and respiratory tract infection. METHODS: This is a population-based retrospective analysis of respiratory virus tests, emergency department (ED) visits and hospitalisations between 2015 and 2021 in Ontario. Weekly virus testing data were used to estimate viral prevalence for all non-COVID-19 respiratory viruses. We plotted the %positivity and observed and expected counts of each virus to visualise the impact of the pandemic. We used Poisson and binomial logistic regression models to estimate the change in %positivity, count of positive viral cases and count of healthcare utilisation during the pandemic. RESULTS: The prevalence of all non-COVID-19 respiratory viruses decreased dramatically during the pandemic compared with prior. Comparing periods, the incidence rate ratio (IRR) for positive cases corresponded to a >90% reduction for non-COVID-19 respiratory viruses except adenovirus and rhino/enterovirus. Asthma-related ED visits and hospital admissions fell by 57% (IRR 0.43 (95% CI 0.37 to 0.48)) and 61% (IRR 0.39 (95% CI 0.33 to 0.46)). COPD-related ED visits and admissions fell by 63% (IRR 0.37 (95% CI 0.30 to 0.45)) and 45% (IRR 0.55 (95% CI 0.48 to 0.62)). Respiratory tract infection ED visits and admissions fell by 85% (IRR 0.15 (95% CI 0.10 to 0.22)), and 85% (IRR 0.15 (95% CI 0.09 to 0.24)). Rather than the usual peaks in disease condition, during the pandemic, healthcare utilisation peaked in October when rhino/enterovirus peaked. CONCLUSIONS: The prevalence of nearly all non-COVID-19 respiratory viruses decreased during the pandemic and was associated with marked reductions in ED visits and hospitalisations. The re-emergence of rhino/enterovirus was associated with increased healthcare utilisation.

Circulating anti-nuclear autoantibodies in COVID-19 survivors predict long COVID symptoms.

BACKGROUND: Autoimmunity has been reported in patients with severe coronavirus disease 2019 (COVID-19). We investigated whether anti-nuclear/extractable-nuclear antibodies (ANAs/ENAs) were present up to a year after infection, and if they were associated with the development of clinically relevant post-acute sequalae of COVID-19 (PASC) symptoms. METHODS: A rapid-assessment line immunoassay was used to measure circulating levels of ANAs/ENAs in 106 convalescent COVID-19 patients with varying acute phase severities at 3, 6 and 12 months post-recovery. Patient-reported fatigue, cough and dyspnoea were recorded at each time point. Multivariable logistic regression model and receiver operating curves were used to test the association of autoantibodies with patient-reported outcomes and pro-inflammatory cytokines. RESULTS: Compared to age- and sex-matched healthy controls (n=22) and those who had other respiratory infections (n=34), patients with COVID-19 had higher detectable ANAs at 3 months post-recovery (p<0.001). The mean number of ANA autoreactivities per individual decreased between 3 and 12 months (from 3.99 to 1.55) with persistent positive titres associated with fatigue, dyspnoea and cough severity. Antibodies to U1-snRNP and anti-SS-B/La were both positively associated with persistent symptoms of fatigue (p<0.028, area under the curve (AUC) 0.86) and dyspnoea (p<0.003, AUC=0.81). Pro-inflammatory cytokines such as tumour necrosis factor (TNF)-α and C-reactive protein predicted the elevated ANAs at 12 months. TNF-α, D-dimer and interleukin-1ß had the strongest association with symptoms at 12 months. Regression analysis showed that TNF-α predicted fatigue (ß=4.65, p=0.004) and general symptomaticity (ß=2.40, p=0.03) at 12 months. INTERPRETATION: Persistently positive ANAs at 12 months post-COVID are associated with persisting symptoms and inflammation (TNF-α) in a subset of COVID-19 survivors. This finding indicates the need for further investigation into the role of autoimmunity in PASC.

Open-chain thiamine analogues as potent inhibitors of thiamine pyrophosphate (TPP)-dependent enzymes.

A common approach to studying thiamine pyrophosphate (TPP)-dependent enzymes is by chemical inhibition with thiamine/TPP analogues which feature a neutral aromatic ring in place of the positive thiazolium ring of TPP. These are potent inhibitors but their preparation generally involves multiple synthetic steps to construct the central ring. We report efficient syntheses of novel, open-chain thiamine analogues which potently inhibit TPP-dependent enzymes and are predicted to share the same binding mode as TPP. We also report some open-chain analogues that inhibit pyruvate dehydrogenase E1-subunit (PDH E1) and are predicted to occupy additional pockets in the enzyme other than the TPP-binding pockets. This opens up new possibilities for increasing the affinity and selectivity of the analogues for PDH, which is an established anti-cancer target.

Furan-based inhibitors of pyruvate dehydrogenase: SAR study, biochemical evaluation and computational analysis.

Suppression of pyruvate dehydrogenase complex (PDHc) is a mechanism for cancer cells to manifest the Warburg effect. However, recent evidence suggests that whether PDHc activity is suppressed or activated depends on the type of cancer. The PDHc E1 subunit (PDH E1) is a thiamine pyrophosphate (TPP)-dependent enzyme, catalysing the first and rate-limiting step of PDHc; thus, there is a need for selective PDH E1 inhibitors. There is, however, inadequate understanding of the structure-activity relationship (SAR) and a lack of inhibitors specific for mammalian PDH E1. Our group have reported TPP analogues as TPP-competitive inhibitors to study the family of TPP-dependent enzymes. Most of these TPP analogues cannot be used to study PDHc in cells because (a) they inhibit all members of the family and (b) they are membrane-impermeable. Here we report derivatives of thiamine/TPP analogues that identify elements distinctive to PDH E1 for selectivity. Based on our SAR findings, we developed a series of furan-based thiamine analogues as potent, selective and membrane-permeable inhibitors of mammalian PDH E1. We envision that our SAR findings and inhibitors will aid work on using chemical inhibition to understand the oncogenic role of PDHc.

Design of thiamine analogues for inhibition of thiamine diphosphate (ThDP)-dependent enzymes: Systematic investigation through Scaffold-Hopping and C2-Functionalisation.

Thiamine diphosphate (ThDP), the bioactive form of vitamin B1, is an essential coenzyme needed for processes of cellular metabolism in all organisms. ThDP-dependent enzymes all require ThDP as a coenzyme for catalytic activity, although individual enzymes vary significantly in substrate preferences and biochemical reactions. A popular way to study the role of these enzymes through chemical inhibition is to use thiamine/ThDP analogues, which typically feature a neutral aromatic ring in place of the positively charged thiazolium ring of ThDP. While ThDP analogues have aided work in understanding the structural and mechanistic aspects of the enzyme family, at least two key questions regarding the ligand design strategy remain unresolved: 1) which is the best aromatic ring? and 2) how can we achieve selectivity towards a given ThDP-dependent enzyme? In this work, we synthesise derivatives of these analogues covering all central aromatic rings used in the past decade and make a head-to-head comparison of all the compounds as inhibitors of several ThDP-dependent enzymes. Thus, we establish the relationship between the nature of the central ring and the inhibitory profile of these ThDP-competitive enzyme inhibitors. We also demonstrate that introducing a C2-substituent onto the central ring to explore the unique substrate-binding pocket can further improve both potency and selectivity.

Iron in airway macrophages and infective exacerbations of chronic obstructive pulmonary disease.

BACKGROUND: Excess pulmonary iron has been implicated in the pathogenesis of lung disease, including asthma and COPD. An association between higher iron content in sputum macrophages and infective exacerbations of COPD has previously been demonstrated. OBJECTIVES: To assess the mechanisms of pulmonary macrophage iron sequestration, test the effect of macrophage iron-loading on cellular immune function, and prospectively determine if sputum hemosiderin index can predict infectious exacerbations of COPD. METHODS: Intra- and extracellular iron was measured in cell-line-derived and in freshly isolated sputum macrophages under various experimental conditions including treatment with exogenous IL-6 and hepcidin. Bacterial uptake and killing were compared in the presence or absence of iron-loading. A prospective cohort of COPD patients with defined sputum hemosiderin indices were monitored to determine the annual rate of severe infectious exacerbations. RESULTS: Gene expression studies suggest that airway macrophages have the requisite apparatus of the hepcidin-ferroportin axis. IL-6 and hepcidin play roles in pulmonary iron sequestration, though IL-6 appears to exert its effect via a hepcidin-independent mechanism. Iron-loaded macrophages had reduced uptake of COPD-relevant organisms and were associated with higher growth rates. Infectious exacerbations were predicted by sputum hemosiderin index (ß = 0.035, p = 0.035). CONCLUSIONS: We demonstrate in-vitro and population-level evidence that excess iron in pulmonary macrophages may contribute to recurrent airway infection in COPD. Specifically, IL-6-dependent iron sequestration by sputum macrophages may result in immune cell dysfunction and ultimately lead to increased frequency of infective exacerbation.

Synthesis of pyrrothiamine, a novel thiamine analogue, and evaluation of derivatives as potent and selective inhibitors of pyruvate dehydrogenase.

Inhibition of thiamine pyrophosphate (TPP)-dependent enzymes with thiamine/TPP analogues that have the central thiazolium ring replaced with other rings is well established, but a limited number of central rings have been reported. We report a novel analogue, pyrrothiamine, with a central pyrrole ring. We further develop pyrrothiamine derivatives as potent and selective inhibitors of pyruvate dehydrogenase, which might have anti-cancer potential.

Inhaled corticosteroids, COPD, and the incidence of lung cancer: a systematic review and dose response meta-analysis.

BACKGROUND: There has been debate on whether inhaled corticosteroids (ICS) reduce the incidence of lung cancer amongst patients with Chronic Obstructive Lung Disease (COPD). We aimed to perform a systematic review and dose-response meta-analysis on available observational data. METHODS: We performed both a dose response and high versus low random effects meta-analysis on observational studies measuring whether lung cancer incidence was lower in patients using ICS with COPD. We report relative risk (RR) with 95% confidence intervals (CI), as well as risk difference. We use the GRADE framework to report our results. RESULTS: Our dose-response suggested a reduction in the incidence of lung cancer for every 500 ug/day of fluticasone equivalent ICS (RR 0.82 [95% 0.68-0.95]). Using a baseline risk of 7.2%, we calculated risk difference of 14 fewer cases per 1000 ([95% CI 24.7-3.8 fewer]). Similarly, our results suggested that for every 1000 ug/day of fluticasone equivalent ICS, there was a larger reduction in incidence of lung cancer (RR 0.68 [0.44-0.93]), with a risk difference of 24.7 fewer cases per 1000 ([95% CI 43.2-5.4 fewer]). The certainty of the evidence was low to very low, due to risk of bias and inconsistency. CONCLUSION: There may be a reduction in the incidence for lung cancer in COPD patients who use ICS. However, the quality of the evidence is low to very low, therefore, we are limited in making strong claims about the true effect of ICS on lung cancer incidence.

Comprehensive Care Management in Conjunction with Sputum Cytometry-Guided Pharmacotherapy in a Post-Discharge Clinic for Patients with COPD.

Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are amongst the most common reasons for hospital admission, and recurrent episodes occur frequently. Comprehensive care management (CCM) strategies have modest effect in preventing re-admissions. The objectives of this study were to examine the utility of optimizing anti-inflammatory therapy guided by sputum cytometry in the post-hospitalization setting, and to assess the feasibility and effectiveness of a clinic combining CCM and sputum-guided therapy. This is an observational study examining patients who received open-label CCM and sputum cytometry-guided pharmacotherapy in a COPD post-discharge clinic. Referral was based on high risk for readmission after hospitalization for AECOPD. The primary outcome was the change in COPD-related healthcare utilization before and after Visit 1, and this was analyzed with a mixed-effects negative binomial model controlling for age, number of follow-up clinic visits, pack years, current smoking and FEV1. Of 138 patients referred to the clinic, 73% attended at least one visit. Mean FEV1 was 42.8 (19.3) % predicted. Of the patients attending clinic, 42.6% produced an adequate sputum sample, and 32.7% had an abnormal sputum. By individual, infectious bronchitis was the most common (25.7%), followed by eosinophilic bronchitis (13.9%). Comparing the 6-months prior to and after the first clinic visit, there was a lower incidence rate ratio after visit 1 for COPD-related healthcare utilization (0.26 (95%CI 0.22,0.33; p < 0.001)). A COPD post-discharge clinic combining sputum-guided treatment and CCM was feasible and associated with a nearly 75% reduction in the incidence of COPD-related healthcare utilization.

Eosinophil-derived IL-13 promotes emphysema.

The inflammatory responses in chronic airway diseases leading to emphysema are not fully defined. We hypothesised that lung eosinophilia contributes to airspace enlargement in a mouse model and to emphysema in patients with chronic obstructive pulmonary disease (COPD).A transgenic mouse model of chronic type 2 pulmonary inflammation (I5/hE2) was used to examine eosinophil-dependent mechanisms leading to airspace enlargement. Human sputum samples were collected for translational studies examining eosinophilia and matrix metalloprotease (MMP)-12 levels in patients with chronic airways disease.Airspace enlargement was identified in I5/hE2 mice and was dependent on eosinophils. Examination of I5/hE2 bronchoalveolar lavage identified elevated MMP-12, a mediator of emphysema. We showed, in vitro, that eosinophil-derived interleukin (IL)-13 promoted alveolar macrophage MMP-12 production. Airspace enlargement in I5/hE2 mice was dependent on MMP-12 and eosinophil-derived IL-4/13. Consistent with this, MMP-12 was elevated in patients with sputum eosinophilia and computed tomography evidence of emphysema, and also negatively correlated with forced expiratory volume in 1 s.A mouse model of chronic type 2 pulmonary inflammation exhibited airspace enlargement dependent on MMP-12 and eosinophil-derived IL-4/13. In chronic airways disease patients, lung eosinophilia was associated with elevated MMP-12 levels, which was a predictor of emphysema. These findings suggest an underappreciated mechanism by which eosinophils contribute to the pathologies associated with asthma and COPD.

Once daily long-acting beta2-agonists and long-acting muscarinic antagonists in a combined inhaler versus placebo for chronic obstructive pulmonary disease.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a respiratory condition causing accumulation of mucus in the airways, cough, and breathlessness; the disease is progressive and is the fourth most common cause of death worldwide. Current treatment strategies for COPD are multi-modal and aim to reduce morbidity and mortality and increase patients' quality of life by slowing disease progression and preventing exacerbations. Fixed-dose combinations (FDCs) of a long-acting beta2-agonist (LABA) plus a long-acting muscarinic antagonist (LAMA) delivered via a single inhaler are approved by regulatory authorities in the USA, Europe, and Japan for the treatment of COPD. Several LABA/LAMA FDCs are available and recent meta-analyses have clarified their utility versus their mono-components in COPD. Evaluation of the efficacy and safety of once-daily LABA/LAMA FDCs versus placebo will facilitate the comparison of different FDCs in future network meta-analyses. OBJECTIVES: We assessed the evidence for once-daily LABA/LAMA combinations (delivered in a single inhaler) versus placebo on clinically meaningful outcomes in patients with stable COPD. SEARCH METHODS: We identified trials from Cochrane Airways' Specialised Register (CASR) and also conducted a search of the US National Institutes of Health Ongoing Trials Register ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization International Clinical Trials Registry Platform (apps.who.int/trialsearch). We searched CASR and trial registries from their inception to 3 December 2018; we imposed no restriction on language of publication. SELECTION CRITERIA: We included parallel-group and cross-over randomised controlled trials (RCTs) comparing once-daily LABA/LAMA FDC versus placebo. We included studies reported as full-text, those published as abstract only, and unpublished data. We excluded very short-term trials with a duration of less than 3 weeks. We included adults (≥ 40 years old) with a diagnosis of stable COPD. We included studies that allowed participants to continue using their ICS during the trial as long as the ICS was not part of the randomised treatment. DATA COLLECTION AND ANALYSIS: Two review authors independently screened the search results to determine included studies, extracted data on prespecified outcomes of interest, and assessed the risk of bias of included studies; we resolved disagreements by discussion with a third review author. Where possible, we used a random-effects model to meta-analyse extracted data. We rated all outcomes using the GRADE (Grades of Recommendation, Assessment, Development and Evaluation) system and presented results in 'Summary of findings' tables. MAIN RESULTS: We identified and included 22 RCTs randomly assigning 8641 people with COPD to either once-daily LABA/LAMA FDC (6252 participants) or placebo (3819 participants); nine studies had a cross-over design. Studies had a duration of between three and 52 weeks (median 12 weeks). The mean age of participants across the included studies ranged from 59 to 65 years and in 21 of 22 studies, participants had GOLD stage II or III COPD. Concomitant inhaled corticosteroid (ICS) use was permitted in all of the included studies (where stated); across the included studies, between 28% to 58% of participants were using ICS at baseline. Six studies evaluated the once-daily combination of IND/GLY (110/50 µg), seven studies evaluated TIO/OLO (2.5/5 or 5/5 µg), eight studies evaluated UMEC/VI (62.5/5, 125/25 or 500/25 µg) and one study evaluated ACD/FOR (200/6, 200/12 or 200/18 µg); all LABA/LAMA combinations were compared with placebo.The risk of bias was generally considered to be low or unknown (insufficient detail provided), with only one study per domain considered to have a high risk of bias except for the domain 'other bias' which was determined to be at high risk of bias in four studies (in three studies, disease severity was greater at baseline in participants receiving LABA/LAMA compared with participants receiving placebo, which would be expected to shift the treatment effect in favour of placebo).Compared to the placebo, the pooled results for the primary outcomes for the once-daily LABA/LAMA arm were as follows: all-cause mortality, OR 1.88 (95% CI 0.81 to 4.36, low-certainty evidence); all-cause serious adverse events (SAEs), OR 1.06 (95% CI 0.88 to 1.28, high-certainty evidence); acute exacerbations of COPD (AECOPD), OR 0.53 (95% CI 0.36 to 0.78, moderate-certainty evidence); adjusted St George's Respiratory Questionnaire (SGRQ) score, MD -4.08 (95% CI -4.80 to -3.36, high-certainty evidence); proportion of SGRQ responders, OR 1.75 (95% CI 1.54 to 1.99). Compared with placebo, the pooled results for the secondary outcomes for the once-daily LABA/LAMA arm were as follows: adjusted trough forced expiratory volume in one second (FEV1), MD 0.20 L (95% CI 0.19 to 0.21, moderate-certainty evidence); adjusted peak FEV1, MD 0.31 L (95% CI 0.29 to 0.32, moderate-certainty evidence); and all-cause AEs, OR 0.95 (95% CI 0.86 to 1.04; high-certainty evidence). No studies reported data for the 6-minute walk test. The results were generally consistent across subgroups for different LABA/LAMA combinations and doses. AUTHORS' CONCLUSIONS: Compared with placebo, once-daily LABA/LAMA (either IND/GLY, UMEC/VI or TIO/OLO) via a combination inhaler is associated with a clinically significant improvement in lung function and health-related quality of life in patients with mild-to-moderate COPD; UMEC/VI appears to reduce the rate of exacerbations in this population. These conclusions are supported by moderate or high certainty evidence based on studies with an observation period of up to one year.