Biomarkers in the Management of Difficult Asthma

Metabolomics in Animal Models of Bronchial Asthma and Its Translational Importance for Clinics

Bronchial asthma is an extremely heterogenous chronic respiratory disorder with several distinct endotypes and phenotypes. These subtypes differ not only in the pathophysiological changes and/or clinical features but also in their response to the treatment. Therefore, precise diagnostics represent a fundamental condition for effective therapy. In the diagnostic process, metabolomic approaches have been increasingly used, providing detailed information on the metabolic alterations associated with human asthma. Further information is brought by metabolomic analysis of samples obtained from animal models. This article summarizes the current knowledge on metabolomic changes in human and animal studies of asthma and reveals that alterations in lipid metabolism, amino acid metabolism, purine metabolism, glycolysis and the tricarboxylic acid cycle found in the animal studies resemble, to a large extent, the changes found in human patients with asthma. The findings indicate that, despite the limitations of animal modeling in asthma, pre-clinical testing and metabolomic analysis of animal samples may, together with metabolomic analysis of human samples, contribute to a novel way of personalized treatment of asthma patients.

Developments in the Management of Severe Asthma in Children and Adolescents: Focus on Dupilumab and Tezepelumab

Severe asthma in children and adolescents exerts a substantial health, financial, and societal burden. Severe asthma is a heterogeneous condition with multiple clinical phenotypes and underlying inflammatory patterns that might be different in individual patients. Various add-on treatments have been developed to treat severe asthma, including monoclonal antibodies (biologics) targeting inflammatory mediators. Biologics that are currently approved to treat children (≥ 6 years of age) or adolescents (≥ 12 years of age) with severe asthma include: anti-immunoglobulin E (omalizumab), anti-interleukin (IL)-5 (mepolizumab), anti-IL5 receptor (benralizumab), anti-IL4/IL13 receptor (dupilumab), and antithymic stromal lymphopoietin (TSLP) (tezepelumab). However, access to these targeted treatments varies across countries and relies on few and crude indicators. There is a need for better treatment stratification to guide which children might benefit from these treatments. In this narrative review we will assess the most recent developments in the treatment of severe pediatric asthma, as well as potential biomarkers to assess treatment efficacy for this patient population.

Phenotype overlap in the natural history of asthma

The heterogeneity of asthma makes it challenging to unravel the pathophysiologic mechanisms of the disease. Despite the wealth of research identifying diverse phenotypes, many gaps still remain in our knowledge of the disease's complexity. A crucial aspect is the impact of airborne factors over a lifetime, which often results in a complex overlap of phenotypes associated with type 2 (T2), non-T2 and mixed inflammation. Evidence now shows overlaps between the phenotypes associated with T2, non-T2 and mixed T2/non-T2 inflammation. These interconnections could be induced by different determinants such as recurrent infections, environmental factors, T-helper plasticity and comorbidities, collectively resulting in a complex network of distinct pathways generally considered as mutually exclusive. In this scenario, we need to abandon the concept of asthma as a disease characterised by distinct traits grouped into static segregated categories. It is now evident that there are multiple interplays between the various physiologic, cellular and molecular features of asthma, and the overlap of phenotypes cannot be ignored.

Delineating asthma according to inflammation phenotypes with a focus on paucigranulocytic asthma

ABSTRACT

Asthma is characterized by chronic airway inflammation and airway hyper-responsiveness. However, the differences in pathophysiology and phenotypic symptomology make a diagnosis of "asthma" too broad hindering individualized treatment. Four asthmatic inflammatory phenotypes have been identified based on inflammatory cell profiles in sputum: eosinophilic, neutrophilic, paucigranulocytic, and mixed-granulocytic. Paucigranulocytic asthma may be one of the most common phenotypes in stable asthmatic patients, yet it remains much less studied than the other inflammatory phenotypes. Understanding of paucigranulocytic asthma in terms of phenotypic discrimination, distribution, stability, surrogate biomarkers, underlying pathophysiology, clinical characteristics, and current therapies is fragmented, which impedes clinical management of patients. This review brings together existing knowledge and ongoing research about asthma phenotypes, with a focus on paucigranulocytic asthma, in order to present a comprehensive picture that may clarify specific inflammatory phenotypes and thus improve clinical diagnoses and disease management.

T2-Low Asthma: A Discussed but Still Orphan Disease

Asthma affects 10% of the worldwide population; about 5% of cases are severe with the need for target therapies such as biologics. All the biologics approved for asthma hit the T2 pathway of inflammation. T2-high asthma is classified as allergic and non-allergic, whereas T2-low asthma can be further defined as paucigranulocytic asthma, Type 1 and Type-17 inflammation and the neutrophilic form that accounts for 20-30% of all patients with asthma. Neutrophilic asthma's prevalence is even higher in patients with severe or refractory asthma. We searched Medline and PubMed archives from the past ten years for articles with the subsequent titles: "neutrophilic asthma", "non-type 2 asthma" and "paucigranulocytic asthma". We identified 177 articles; 49 were considered relevant by the title and 33 by the reading of the abstract. Most of these articles are reviews (n = 19); only 6 are clinical trials. No study identified an effective treatment. We used the literature reported by these articles to search for further biologic treatments that target pathways different from T2. We identified 177 articles, 93 of which were considered relevant for the review and included in the present article. In conclusion, T2-low asthma remains poorly investigated in terms of biomarkers, especially as a therapeutic orphan disease.

Severe Asthmatic Responses: The Impact of TSLP

Asthma is a chronic inflammatory disease that affects the lower respiratory system and includes several categories of patients with varying features or phenotypes. Patients with severe asthma (SA) represent a group of asthmatics that are poorly responsive to medium-to-high doses of inhaled corticosteroids and additional controllers, thus leading in some cases to life-threatening disease exacerbations. To elaborate on SA heterogeneity, the concept of asthma endotypes has been developed, with the latter being characterized as T2-high or low, depending on the type of inflammation implicated in disease pathogenesis. As SA patients exhibit curtailed responses to standard-of-care treatment, biologic therapies are prescribed as adjunctive treatments. To date, several biologics that target specific downstream effector molecules involved in disease pathophysiology have displayed superior efficacy only in patients with T2-high, eosinophilic inflammation, suggesting that upstream mediators of the inflammatory cascade could constitute an attractive therapeutic approach for difficult-to-treat asthma. One such appealing therapeutic target is thymic stromal lymphopoietin (TSLP), an epithelial-derived cytokine with critical functions in allergic diseases, including asthma. Numerous studies in both humans and mice have provided major insights pertinent to the role of TSLP in the initiation and propagation of asthmatic responses. Undoubtedly, the magnitude of TSLP in asthma pathogenesis is highlighted by the fact that the FDA recently approved tezepelumab (Tezspire), a human monoclonal antibody that targets TSLP, for SA treatment. Nevertheless, further research focusing on the biology and mode of function of TSLP in SA will considerably advance disease management.

Identification of hub genes and potential biomarkers of neutrophilic asthma: evidence from a bioinformatics analysis

OBJECTIVE

Asthma is a chronic airway inflammatory disease caused by multiple genetic and environmental factors. This study mainly sought to provide potential therapeutic targets and biomarkers for neutrophilic asthma (NA).

METHODS

Three gene expression profiling datasets were obtained from the Genome Expression Omnibus (GEO) database. GSE45111 and GSE41863 were used to identify hub genes and potential biomarkers, and GSE137268 was used for data verification. We verified the repeatability of intragroup data and identified differentially expressed genes (DEGs). Then, we conducted Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of the DEGs, and a protein-protein interaction (PPI) network was constructed to identify the hub genes. Finally, receiver operating characteristic (ROC) analysis was used to verify the ability of the hub genes to differentiate between NA and eosinophilic asthma (EA).

RESULTS

In this study, we identified 411 DEGs by comprehensive analysis of NA/EA patients and NA/healthy controls (HCs). Ten hub genes (CXCR1, FCGR3B, CXCR2, SELL, S100A12, CSF3R, IL6R, JAK3, CD48, and GNG2) were identified from the PPI network. Finally, based on the ROC analysis, 7 genes showed good diagnostic value for discriminating NA from EA-CXCR1, FCGR3B, CXCR2, SELL, S100A12, CSF3R, and IL6R (AUC > 0.7).

CONCLUSION

We identified 7 hub genes that can distinguish NA from EA. The IL-8-mediated signaling may be the primary pathway to determine the NA phenotype in asthma. CXCR1/2 and S100A12 may be the primary genes determining the NA phenotype. CXCR1/2 and S100A12 might be biomarkers and new therapeutic targets for NA.

Supplemental data for this article is available online at at.

How does cigarette smoking affect airway remodeling in asthmatics?

Asthma is a prevalent chronic airway inflammatory disease involving multiple cells, and the prolonged course of the disease can cause airway remodeling, resulting in irreversible or partial irreversible airflow limitation and persistent airway hyperresponsiveness (AHR) in asthmatics. Therefore, we must ascertain the factors that affect the occurrence and development of airway remodeling in asthmatics. Smokers are not uncommon in asthmatics. However, there is no systematic description of how smoking promotes airway remodeling in asthmatics. This narrative review summarizes the effects of smoking on airway remodeling in asthmatics, and the progress of the methods for evaluating airway remodeling.

Baseline type 2 biomarker levels and response to tezepelumab in severe asthma

Background

Tezepelumab is a human monoclonal antibody that blocks activity of thymic stromal lymphopoietin (TSLP). In the phase IIb PATHWAY study (NCT02054130), tezepelumab significantly reduced annualized asthma exacerbation rates (AAERs) versus placebo in adults with severe, uncontrolled asthma. We evaluated the effects of tezepelumab in reducing type 2 (T2) inflammatory biomarker levels in the PATHWAY population, and the relationship between baseline T2 biomarker levels and AAER.

Methods

Adults with severe, uncontrolled asthma (n = 550) were randomized to tezepelumab (70 mg or 210 mg every 4 weeks, or 280 mg every 2 weeks) or placebo for 52 weeks. Blood eosinophil count, fractional exhaled nitric oxide (FeNO), and serum total immunoglobulin (Ig)E, interleukin (IL)‐5, IL‐13, periostin, thymus and activation‐regulated chemokine (TARC), and TSLP were measured at baseline and over 52 weeks. AAERs were analyzed by baseline threshold (high/low) biomarker levels.

Results

Positive correlations were observed between T2 inflammatory biomarkers (blood eosinophil count, FeNO, IL‐5, IL‐13 and periostin) at baseline. At Week 52, treatment with tezepelumab 210 mg reduced all biomarker levels measured from baseline versus placebo. Exacerbations were reduced by 55–83% in the pooled tezepelumab cohort versus placebo, irrespective of baseline blood eosinophil count, FeNO, or serum total IgE, IL‐5, IL‐13, periostin, TARC, or TSLP, when these biomarkers were assessed individually.

Conclusion

At baseline, positive correlations between specific T2 inflammatory biomarkers were observed. Tezepelumab reduced multiple T2 inflammatory biomarkers, which indicates decreased airway inflammation, and reduced exacerbations irrespective of baseline T2 biomarker profiles in patients with severe asthma.

Dupilumab efficacy and safety in patients with asthma and blood eosinophils ≥500 cells·µL-1

Uncontrolled, moderate-to-severe asthma in patients with high baseline blood eosinophils (≥500 cells·µL⁻¹) can be difficult to treat [1]. Global Initiative for Asthma guidelines recommend biologics as add-on therapy for patients with severe type 2 inflammatory asthma that remains uncontrolled despite treatment with high-dose inhaled corticosteroids [2]. Surrogate markers of type 2 inflammation, such as elevated levels of blood or sputum eosinophils and fractional exhaled nitric oxide (F_eNO) can be used to identify patients with a type 2 signature who might be eligible for such treatment [1–3]. Several biologics are now available that target different molecules in type 2 inflammatory pathways, notably IgE and type 2 cytokines [1–3]. One of these, dupilumab, is a fully human VelocImmune-derived [4, 5] monoclonal antibody that blocks the shared receptor component for interleukin-4 and -13, cytokines that are key and central drivers of type 2 inflammation in multiple diseases, thus inhibiting their signalling [6, 7].

Dupilumab is well tolerated and improves clinical outcomes in patients with asthma and high eosinophils (≥500 cells·µL⁻¹). Improvements in clinical outcomes correlate with eosinophil counts, demonstrating dupilumab efficacy in those with high eosinophils.https://bit.ly/3Jxvicb

Identification of Key Signaling Pathways and Genes in Eosinophilic Asthma and Neutrophilic Asthma by Weighted Gene Co-Expression Network Analysis

Background: Asthma is a heterogeneous disease with different subtypes including eosinophilic asthma (EA) and neutrophilic asthma (NA). However, the mechanisms underlying the difference between the two subtypes are not fully understood.

Methods: Microarray datasets (GSE45111 and GSE137268) were acquired from Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) in induced sputum between EA (n = 24) and NA (n = 15) were identified by “Limma” package. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses and Gene set enrichment analysis (GSEA) were used to explore potential signaling pathways. Weighted gene co-expression network analysis (WGCNA) were performed to identify the key genes that were strongly associated with EA and NA.

Results: A total of 282 DEGs were identified in induced sputum of NA patients compared with EA patients. In GO and KEGG pathway analyses, DEGs were enriched in positive regulation of cytokine production, and cytokine-cytokine receptor interaction. The results of GSEA showed that ribosome, Parkinson’s disease, and oxidative phosphorylation were positively correlated with EA while toll-like receptor signaling pathway, primary immunodeficiency, and NOD-like receptor signaling pathway were positively correlated with NA. Using WGCNA analysis, we identified a set of genes significantly associated NA including IRFG, IRF1, STAT1, IFIH1, IFIT3, GBP1, GBP5, IFIT2, CXCL9, and CXCL11.

Conclusion: We identified potential signaling pathways and key genes involved in the pathogenesis of the asthma subsets, especially in neutrophilic asthma.

Which Therapy for Non-Type(T)2/T2-Low Asthma

Currently, the asthmatic population is divided into Type 2-high and non-Type 2/Type 2-low asthmatics, with 50% of patients belonging to one of the two groups. Differently from T2-high, T2-low asthma has not been clearly defined yet, and the T2-low patients are identified on the basis of the absence or non-predominant expression of T2-high biomarkers. The information about the molecular mechanisms underpinning T2-low asthma is scarce, but researchers have recognized as T2-low endotypes type 1 and type 3 immune response, and remodeling events occurring without inflammatory processes. In addition, the lack of agreed biomarkers reprents a challenge for the research of an effective therapy. The first-choice medication is represented by inhaled corticosteroids despite a low efficacy is reported for/in T2-low patients. However, macrolides and long-acting anti-muscarinic drugs have been recognized as efficacious. In recent years, clinical trials targeting biomarkers playing key roles in T3 and T1 immune pathways, alarmins, and molecules involved in neutrophil recruitment have provided conflicting results probably misleading (or biased) in patients' selection. However, further studies are warranted to achieve a precise characterization of T2-low asthma with the aim of defining a tailored therapy for each single asthmatic patient.

Plasma proteins elevated in severe asthma despite oral steroid use and unrelated to Type-2 inflammation

Rationale

Asthma phenotyping requires novel biomarker discovery.

Objectives

To identify plasma biomarkers associated with asthma phenotypes by application of a new proteomic panel to samples from two well-characterised cohorts of severe (SA) and mild-to-moderate (MMA) asthmatics, COPD subjects and healthy controls (HCs).

Methods

An antibody-based array targeting 177 proteins predominantly involved in pathways relevant to inflammation, lipid metabolism, signal transduction and extracellular matrix was applied to plasma from 525 asthmatics and HCs in the U-BIOPRED cohort, and 142 subjects with asthma and COPD from the validation cohort BIOAIR. Effects of oral corticosteroids (OCS) were determined by a 2-week, placebo-controlled OCS trial in BIOAIR, and confirmed by relation to objective OCS measures in U-BIOPRED.

Results

In U-BIOPRED, 110 proteins were significantly different, mostly elevated, in SA compared to MMA and HCs. 10 proteins were elevated in SA versus MMA in both U-BIOPRED and BIOAIR (alpha-1-antichymotrypsin, apolipoprotein-E, complement component 9, complement factor I, macrophage inflammatory protein-3, interleukin-6, sphingomyelin phosphodiesterase 3, TNF receptor superfamily member 11a, transforming growth factor-β and glutathione S-transferase). OCS treatment decreased most proteins, yet differences between SA and MMA remained following correction for OCS use. Consensus clustering of U-BIOPRED protein data yielded six clusters associated with asthma control, quality of life, blood neutrophils, high-sensitivity C-reactive protein and body mass index, but not Type-2 inflammatory biomarkers. The mast cell specific enzyme carboxypeptidase A3 was one major contributor to cluster differentiation.

Conclusions

The plasma proteomic panel revealed previously unexplored yet potentially useful Type-2-independent biomarkers and validated several proteins with established involvement in the pathophysiology of SA.

Application of new proteomic panel in two established European asthma cohorts identifies plasma proteins associated with disease severity independently of Type-2 inflammation, suggesting potentially useful novel biomarkers and therapeutic targets.https://bit.ly/3jtTq5m

Paucigranulocytic asthma: Do sputum macrophages matter?

Background: Although paucigranulocytic asthma (PGA) is the most common phenotype of stable asthma, its features have not been adequately studied. In this study, we aimed to display the characteristics of PGA. Method: A total of 116 non-smoking adult patients with asthma (80% women; mean ± standard deviation age, 39 ± 12.9 years) admitted to three tertiary centers were included. Their demographic and clinical features, allergy status, biochemical results, scores of Asthma Control Test (ACT), spirometry, and exhaled nitric oxide (FeNO) measurements were obtained. Induced sputum cytometry was performed. Results: Four phenotypes, according to induced sputum cell counts, were detected: eosinophilic asthma (EA) (22.4%), mixed granulocytic asthma (MGA) (6.9%), neutrophilic (NA) (7.8%), and PGA (62.9%). In the sputum, macrophages were higher in the PGA group compared with the other groups (PGA versus NA and PGA versus MGA, p < 0.001; and PGA versus EA, p =0 .030). The atopy rate between phenotypes was the same. Although the forced expiratory volume in the first second of expiration (FEV₁) was similar in four groups, the ratio of FEV₁ to the forced vital capacity ratio was higher (p = 0.013) and FEV₁ reversibility was lower in the patients with PGA than the corresponding values in other phenotypes (p = 0.015). Low reversibility was comparable both in patients with PGA who were inhaled corticosteroid (ICS) naive and in patients on ICS treatment. Although insignificant, the FeNO values and blood eosinophil counts were higher in the MGA and EA groups, whereas these were the lowest in the PGA group. The uncontrolled asthma ratio was low in PGA (16%), whereas it was 11% for NA, 25% for MG, and 23% in EA. Conclusion: Macrophages are predominant in sputum of patients with PGA. Besides a lower uncontrolled asthma ratio, lower FEV₁ reversibility is a prominent characteristic of this phenotype.

Latest Progresses in Allergic Diseases Biomarkers: Asthma and Atopic Dermatitis

In the last years, the understanding of the pathologic mechanisms of asthma and atopic dermatitis, both characterized by allergic inflammation, has greatly improved. However, it is evident that both diseases present with high heterogeneity, which complicates the diagnosis and the therapeutic approach of the patients. Moreover, some of the currently available strategies to treat asthma and atopic dermatitis are still mostly controlling the symptoms, but not to lead towards full healing, thus having these two diseases labelled as unmet clinical needs by WHO. Therefore, the "one-size-fits-all" strategy is outdated for asthma and atopic dermatitis, and there is the need of better methods to clearly diagnose the disease and tailor the therapy according to the specific symptomatology. In this regard, the use of biomarkers has been advanced in order to characterize both diseases according to their clinical signs and to facilitate the subsequent treatment. Despite the advancements made in this regard, there is still need for better and more sensitive biomarkers and for less invasive sampling methodologies, with the aim to diagnose specifically each manifestation of asthma and atopic dermatitis and to provide the best treatment with the least suffering for the patients.

Metabolomics, Microbiota, and In Vivo and In Vitro Biomarkers in Type 2 Severe Asthma: A Perspective Review

Precision medicine refers to the tailoring of therapeutic strategies to the individual characteristics of each patient; thus, it could be a new approach for the management of severe asthma that considers individual variability in genes, environmental exposure, and lifestyle. Precision medicine would also assist physicians in choosing the right treatment, the best timing of administration, consequently trying to maximize drug efficacy, and, possibly, reducing adverse events. Metabolomics is the systematic study of low molecular weight (bio)chemicals in a given biological system and offers a powerful approach to biomarker discovery and elucidating disease mechanisms. In this point of view, metabolomics could play a key role in targeting precision medicine.

Metabolomics, Microbiota, and In Vivo and In Vitro Biomarkers in Type 2 Severe Asthma: A Perspective Review

Precision medicine refers to the tailoring of therapeutic strategies to the individual characteristics of each patient; thus, it could be a new approach for the management of severe asthma that considers individual variability in genes, environmental exposure, and lifestyle. Precision medicine would also assist physicians in choosing the right treatment, the best timing of administration, consequently trying to maximize drug efficacy, and, possibly, reducing adverse events. Metabolomics is the systematic study of low molecular weight (bio)chemicals in a given biological system and offers a powerful approach to biomarker discovery and elucidating disease mechanisms. In this point of view, metabolomics could play a key role in targeting precision medicine.

Elevated serum calprotectin (S100A8/A9) in patients with severe asthma

OBJECTIVE

Asthma is a heterogeneous disease consisting of several inflammatory phenotypes of which neutrophilic asthma is associated with poorer responses to classic therapies, namely (inhaled) corticosteroids. The development of targeted therapies requires the identification of biomarkers to distinguish these phenotypes. Currently, we lack validated biomarkers for non-eosinophilic asthma. The aim of this study is to examine serum calprotectin (SC) in asthmatics and its potential as biomarker for neutrophilic asthma.

METHODS

Hundred-seventeen severe asthmatics were referred for sputum induction and data were obtained from their medical records. To evaluate the association between SC and asthma phenotypes, patients were divided into subgroups based on sputum cell count (3% eosinophils and 61% neutrophils). Additionally, SC levels of asthmatics were compared with these of patients with chronic obstructive pulmonary disease, non-cystic fibrosis bronchiectasis and healthy controls.

RESULTS

Asthmatics (n = 45) had significantly higher levels of SC than healthy controls. No significant differences were found between the different asthma phenotypes and in comparison with COPD patients. SC was significantly higher in asthmatics with a lower FEV₁/FVC ratio (<70) and non-significantly elevated SC levels were seen in asthmatics with frequent exacerbations (>2 in the last year).

CONCLUSION

In conclusion, there was no difference in SC levels between the different inflammatory subtypes in asthmatics. Nevertheless, severe asthmatics seemed to have higher SC levels suggesting that SC may be a marker of disease severity rather than a marker for specific inflammatory subtypes in asthmatics. Further research in larger cohorts is necessary to validate SC as biomarker in severe asthmatics.

The central role of IL-33/IL-1RL1 pathway in asthma: From pathogenesis to intervention

Interleukin-33 (IL-33), a member of the IL-1 family, and its cognate receptor, Interleukin-1 receptor like-1 (IL-1RL1 or ST2), are susceptibility genes for childhood asthma. In response to cellular damage, IL-33 is released from barrier tissues as an 'alarmin' to activate the innate immune response. IL-33 drives type 2 responses by inducing signalling through its receptor IL-1RL1 in several immune and structural cells, thereby leading to type 2 cytokine and chemokine production. IL-1RL1 gene transcript encodes different isoforms generated through alternative splicing. Its soluble isoform, IL-1RL1-a or sST2, acts as a decoy receptor by sequestering IL-33, thereby inhibiting IL1RL1-b/IL-33 signalling. IL-33 and its receptor IL-1RL1 are therefore considered as putative biomarkers or targets for pharmacological intervention in asthma. This review will provide an overview of the genetics and biology of the IL-33/IL-1RL1 pathway in the context of asthma pathogenesis. It will discuss the potential and complexities of targeting the cytokine or its receptor, how genetics or biomarkers may inform precision medicine for asthma targeting this pathway, and the possible positioning of therapeutics targeting IL-33 or its receptor in the expanding landscape of novel biologicals applied in asthma management.

An update on the diagnostic biomarkers for asthma

Asthma is a respiratory disorder accounts for ~339 million cases per annum. The initial diagnosis of asthma relies on the symptomatic identification of characters, such as wheeze, shortness of breath, chest tightness, and cough. The presence of two or more of these symptoms may be considered as indicative of asthma. The asthma-diagnostic also involves spirometry test before and after inhaling a bronchodilator like albuterol. Because asthma pathophysiology involves participation of immune system, the cytokines play an important role. The review discusses various molecules that are or may be used as biomarkers for the asthma diagnosis.

Tezepelumab improves patient-reported outcomes in patients with severe, uncontrolled asthma in PATHWAY

BACKGROUND

Patients with severe, uncontrolled asthma experience frequent exacerbations and hospitalization, leading to poor health-related quality of life. In the phase 2b PATHWAY study (NCT02054130), tezepelumab reduced exacerbations by up to 71% and improved lung function, asthma control, and health-related quality of life vs placebo.

OBJECTIVE

This analysis further assessed the impact of tezepelumab on patient-reported outcomes (PROs) in PATHWAY.

METHODS

Adults with severe, uncontrolled asthma were randomized to subcutaneous tezepelumab (70 mg every 4 weeks, 210 mg every 4 weeks, or 280 mg every 2 weeks) or placebo for 52 weeks. PROs were assessed using the asthma control questionnaire-6 (ACQ-6) and the asthma quality of life questionnaire (standardized) for patients aged 12 years or older (AQLQ[S]+12). The proportions of responders (defined by improvements of ≥0.5 in ACQ-6 or AQLQ(S)+12 scores) and patients whose asthma was well-controlled, partially-controlled, or uncontrolled in the tezepelumab and placebo groups were identified. The Asthma Daily Diary questionnaire was used to assess changes in overall symptom severity.

RESULTS

Overall, 550 patients were randomized. Up to 82% and 77% of tezepelumab-treated patients were ACQ-6 and AQLQ(S)+12 responders, respectively, compared with 70% and 64% of placebo-treated patients, respectively. The proportions of patients with well-controlled or partially-controlled asthma were higher in the tezepelumab-treated group than in the placebo group. In addition, tezepelumab improved the overall symptom severity.

CONCLUSION

Tezepelumab treatment improved PROs vs placebo, as indicated by the higher proportion of ACQ-6 and AQLQ(S)+12 responders and improvements in symptom severity in the tezepelumab dose groups. These data further support the benefits of tezepelumab in patients with severe, uncontrolled asthma.

Airway G-CSF identifies neutrophilic inflammation and contributes to asthma progression

Stratification of asthmatic patients based on relevant biomarkers enables the prediction of responsiveness against immune-targeted therapies in patients with asthma. Individualised therapy in patients with eosinophilic asthma has yielded improved clinical outcomes; similar approaches in patients with neutrophilic asthma have yet to be developed. We determined whether colony-stimulating factors (CSFs) in the airway reflect the inflammatory phenotypes of asthma and contribute to disease progression of neutrophilic asthma.We analysed three different mouse models of asthma and assessed cytokine profiles in sputum from human patients with asthma stratified according to inflammatory phenotype. In addition, we evaluated the therapeutic efficacy of various cytokine blockades in a mouse model of neutrophilic asthma.Among the CSFs, airway granulocyte CSF (G-CSF) contributes to airway neutrophilia by promoting neutrophil development in bone marrow and thereby distinguishes neutrophilic inflammation from eosinophilic inflammation in mouse models of asthma. G-CSF is produced by concurrent stimulation of the lung epithelium with interleukin (IL)-17A and tumour necrosis factor (TNF)-α; therefore, dual blockade of upstream stimuli using monoclonal antibodies or genetic deficiency of the cytokines in IL-17A×TNF-α double-knockout mice reduced the serum level of G-CSF, leading to alleviation of neutrophilic inflammation in the airway. In humans, the sputum level of G-CSF can be used to stratify patients with asthma with neutrophil-dominated inflammation.Our results indicated that myelopoiesis-promoting G-CSF and cytokines as the upstream inducing factors are potential diagnostic and therapeutic targets in patients with neutrophilic asthma.

Asthma and Corticosteroid Responses in Childhood and Adult Asthma

Corticosteroids are the most effective treatment for asthma; inhaled corticosteroids (ICSs) are the first-line treatment for children and adults with persistent symptoms. ICSs are associated with significant improvements in lung function. The anti-inflammatory effects of corticosteroids are mediated by both genomic and nongenomic factors. Variation in the response to corticosteroids has been observed. Patient characteristics, biomarkers, and genetic features may be used to predict response to ICSs. The existence of multiple mechanisms underlying glucocorticoid insensitivity raises the possibility that this might indeed reflect different diseases with a common phenotype.

Immunological biomarkers in severe asthma

Severe asthma is heterogeneous in its clinical presentation, underlying pathophysiology, course and response to therapy. Clinical and physiological assessment of severe asthma is often inadequate in predicting underlying disease mechanisms and or response to medications. With the emergence of novel targeted therapies in severe asthma, the need for reproducible, easily measured biomarkers became obvious but only few are currently available for clinical use. These biomarkers along with the clinical presentation of the patient play an important role in identifying phenotypes and endotypes, predicting the clinical course and prognosis and improving the precision therapeutic approach to asthma.

Serum levels of epithelial-derived mediators and interleukin-4/interleukin-13 signaling after bronchial challenge with Dermatophagoides pteronyssinus in patients with allergic asthma

Allergens are the main trigger that enhances airway type 2 inflammation, and the epithelium is the first line of defense that reacts to its exposure. Therefore, epithelial-derived mediators, such as interleukin (IL)-25, IL-33, thymic stromal lymphopoietin (TSLP) and ezrin, may play a role as alarmins in IL-4/IL-13 signaling in allergic asthma (AA). We investigated the serum levels of IL-25, IL-33, TSLP, ezrin, IL-4 and IL-13, after bronchial challenge with Dermatophagoides pteronyssinus in patients with AA. We examined 18 subjects: nine steroid-free stable patients with AA sensitized to D. pteronyssinus and nine non-atopic healthy subjects (HS). Bronchial allergen challenge was performed using inhaled D. pteronyssinus allergen. IL-4, IL-13, IL-25, IL-33, TSLP and ezrin levels in serum were measured by ELISA at two time points - before and 24 hours after bronchial allergen challenge. The serum levels of IL-25, TSLP and ezrin did not differ between AA and HS groups at baseline. However, after allergen exposure, significant increases in serum levels of IL-25, TSLP and ezrin were observed only in patients with AA. The serum level of IL-33 at baseline was significantly higher in the AA group compared with HS, but the allergen challenge did not provoke an increase of this cytokine in any group. IL-4 and IL-13 levels were significantly higher at baseline in the AA group compared with HS and, after allergen exposure, were significantly increased in the AA group, with no effect on HS. Thus, the epithelial-derived mediators IL-25, TSLP and ezrin, via IL4/IL13 signaling, enhance type 2 inflammation after bronchial challenge with D. pteronyssinus in AA.

Targeting NLRP3 Inflammasome Activation in Severe Asthma

Severe asthma (SA) is a chronic lung disease characterized by recurring symptoms of reversible airflow obstruction, airway hyper-responsiveness (AHR), and inflammation that is resistant to currently employed treatments. The nucleotide-binding oligomerization domain-like Receptor Family Pyrin Domain Containing 3 (NLRP3) inflammasome is an intracellular sensor that detects microbial motifs and endogenous danger signals and represents a key component of innate immune responses in the airways. Assembly of the NLRP3 inflammasome leads to caspase 1-dependent release of the pro-inflammatory cytokines IL-1β and IL-18 as well as pyroptosis. Accumulating evidence proposes that NLRP3 activation is critically involved in asthma pathogenesis. In fact, although NLRP3 facilitates the clearance of pathogens in the airways, persistent NLRP3 activation by inhaled irritants and/or innocuous environmental allergens can lead to overt pulmonary inflammation and exacerbation of asthma manifestations. Notably, administration of NLRP3 inhibitors in asthma models restrains AHR and pulmonary inflammation. Here, we provide an overview of the pathophysiology of SA, present molecular mechanisms underlying aberrant inflammatory responses in the airways, summarize recent studies pertinent to the biology and functions of NLRP3, and discuss the role of NLRP3 in the pathogenesis of asthma. Finally, we contemplate the potential of targeting NLRP3 as a novel therapeutic approach for the management of SA.

Exhaled volatile organic compounds in adult asthma: a systematic review

The search for biomarkers that can guide precision medicine in asthma, particularly those that can be translated to the clinic, has seen recent interest in exhaled volatile organic compounds (VOCs). Given the number of studies reporting "breathomics" findings and its growing integration in clinical trials, we performed a systematic review of the literature to summarise current evidence and understanding of breathomics technology in asthma.A PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses)-oriented systematic search was performed (CRD42017084145) of MEDLINE, Embase and the Cochrane databases to search for any reports that assessed exhaled VOCs in adult asthma patients, using the following terms (asthma AND (volatile organic compounds AND exhaled) OR breathomics).Two authors independently determined the eligibility of 2957 unique records, of which 66 underwent full-text review. Data extraction and risk of bias assessment was performed on the 22 studies deemed to fulfil the search criteria. The studies are described in terms of methodology and the evidence narratively summarised under the following clinical headings: diagnostics, phenotyping, treatment stratification, treatment monitoring and exacerbation prediction/assessment.Our review found that most studies were designed to assess diagnostic potential rather than focus on underlying biology or treatable traits. Results are generally limited by a lack of methodological standardisation and external validation and by insufficiently powered studies, but there is consistency across the literature that exhaled VOCs are sensitive to underlying inflammation. Modern studies are applying robust breath analysis workflows to large multi-centre study designs, which should unlock the full potential of measurement of exhaled volatile organic compounds in airways diseases such as asthma.

Features of Oxidative and Nitrosative Metabolism in Lung Diseases

Respiratory diseases are accompanied by intensification of free radical processes at different levels of the biological body organization. Simultaneous stress and suppression of various parts of antioxidant protection lead to the development of oxidative stress (OS) and nitrosative stress (NS). The basic mechanisms of initiation and development of the OS and NS in pulmonary pathology are considered. The antioxidant defense system of the respiratory tract is characterized. The results of the NS and OS marker study in various respiratory diseases are presented. It is shown that NS and OS are multilevel complex-regulated processes, existing and developing in inseparable connection with a number of physiological and pathophysiological processes. The study of NS and OS mechanisms contributes to the improvement of the quality of diagnosis and the development of therapeutic agents that act on different pathogenetic stages of the disease.

Biomarkers in asthma: state of the art

Asthma is a heterogenous disease characterized by multiple phenotypes driven by different mechanisms. The implementation of precision medicine in the management of asthma requires the identification of phenotype-specific markers measurable in biological fluids. To become useful, these biomarkers need to be quantifiable by reliable systems, reproducible in the clinical setting, easy to obtain and cost-effective. Using biomarkers to predict asthma outcomes and therapeutic response to targeted therapies has a great clinical significance, particularly in severe asthma. In the last years, significant research has been realized in the identification of valid biomarkers for asthma. This review focuses on the existent and emerging biomarkers with clinical higher applicability in the management of asthma.

Biomarker-based corticosteroid adjustment in severe asthma: a modified Delphi consensus

Asthma is managed using “step-wise” adjustment of corticosteroid therapy to achieve asthma control. When corticosteroid treatment is adjusted using sputum eosinophil count or exhaled nitric oxide fraction, exacerbations are reduced [1, 2]; however, implementation in clinical care has been slow. In parallel, airway transcriptomic analysis has demonstrated that type 2 eosinophilic inflammation is absent in many patients with minimal response to corticosteroid treatment [3–5]. The UK Refractory Asthma Stratification Programme (RASP-UK) (http://rasp.org.uk/) is exploring non-sputum biomarker-based strategies to target corticosteroid treatment in severe asthma [6, 7], and sought to determine clinician and patient views on clinically relevant reductions in corticosteroid treatment.

UK asthma physicians are supportive of biomarker-based steroid adjustment, but European physicians need more evidencehttp://ow.ly/sTrf30my3jw

Omalizumab for Severe Asthma: Beyond Allergic Asthma

Different subsets of asthma patients may be recognized according to the exposure trigger and the frequency and severity of clinical signs and symptoms. Regarding the exposure trigger, generally asthma can be classified as allergic (or atopic) and nonallergic (or nonatopic). Allergic and nonallergic asthma are distinguished by the presence or absence of clinical allergic reaction and in vitro IgE response to specific aeroallergens. The mechanisms of allergic asthma have been extensively studied with major advances in the last two decades. Nonallergic asthma is characterized by its apparent independence from allergen exposure and sensitization and a higher degree of severity, but little is known regarding the underlying mechanisms. Clinically, allergic and nonallergic asthma are virtually indistinguishable in exacerbations, although exacerbation following allergen exposure is typical of allergic asthma. Although they both show several distinct clinical phenotypes and different biomarkers, there are no ideal biomarkers to stratify asthma phenotypes and guide therapy in clinical practice. Nevertheless, some biomarkers may be helpful to select subsets of atopic patients which might benefit from biologic agents, such as omalizumab. Patients with severe asthma, uncontrolled besides optimal treatment, notwithstanding nonatopic, may also benefit from omalizumab therapy, although currently there are no randomized double-blind placebo controlled clinical trials to support this suggestion. However, omalizumab discontinuation according to each patient's response to therapy and pharmacoeconomical analysis are questions that remain to be answered.

Paucigranulocytic asthma: Uncoupling of airway obstruction from inflammation

Among patients with asthma, heterogeneity exists regarding the pattern of airway inflammation and response to treatment, prompting the necessity of recognizing specific phenotypes. Based on the analysis of inflammatory cell counts in induced sputum, asthmatic patients can be classified into 4 unique phenotypes: eosinophilic asthma, neutrophilic asthma, mixed granulocytic asthma, and paucigranulocytic asthma (PGA). PGA is an asthma phenotype with no evidence of increased numbers of eosinophils or neutrophils in sputum or blood and in which anti-inflammatory therapies are ineffective at controlling symptoms. Although underinvestigated, PGA is the most common asthma phenotype in patients with stable asthma. However, PGA is sometimes underestimated because of the exclusive reliance on induced sputum cell counts, which are variable among cohorts of studies, prompting the necessity of developing improved biomarkers. Importantly, investigators have reported that inhaled corticosteroids had a limited effect on airway inflammatory markers in patients with PGA and therefore defining PGA as a potentially "steroid-insensitive" phenotype that requires exploration of alternative therapies. PGA manifests as an uncoupling of airway obstruction from airway inflammation that can be driven by structural changes within the airways, such as airway smooth muscle tissue hypertrophy. Animal models provide evidence that processes evoking airway hyperresponsiveness and airway smooth muscle thickening occur independent from inflammation and might be a consequence of a loss of negative homeostatic processes. Collectively, further understanding of PGA with a focus on the characterization, prevalence, clinical significance, and pathobiology derived from animal studies will likely provide precision therapies that will improve PGA clinical outcomes.

Asthma and its comorbidities in middle-aged and older adults; the Rotterdam Study

BACKGROUND

Little is known on the prevalence and characteristics of asthma in middle-aged and older adults, since previous studies mainly focused on children and young adults. Therefore, the aim was to investigate the prevalence of physician-diagnosed asthma and its comorbidities, in a population-based cohort of adults 45 years of age and over.

METHODS

We identified participants with physician-diagnosed asthma in the Rotterdam Study; a prospective population-based cohort in the Netherlands. Pulmonary function measurements and comorbidities of the asthma cases were assessed at baseline and compared to those of the general population.

RESULTS

Out of 14,621 participants (mean age 65.5 years; 59% women), 524 subjects (31.5%males) had physician-diagnosed asthma at study entry, implicating an asthma prevalence of 3.6% [95% Confidence Interval (CI) 3.3%-3.9%] (2.8% in males and 4.2% in females). Asthmatic subjects had a significantly higher prevalence of obesity and depressive symptoms (Odds Ratio [OR]: 2,02 [95% CI 1,66-2,47] and [OR]: 2,01 [95% CI 1,52-2,66] respectively). Longer duration of asthma and current smoking were associated with lower lung function in asthmatic subjects.

CONCLUSION

Four percent of middle-aged and older adults have physician-diagnosed asthma. These adult asthmatics suffer more frequently from obesity and depression than subjects without obstructive lung disease.

T2-low asthma: current approach to diagnosis and therapy

PURPOSE OF REVIEW

Asthma is a heterogeneous disease not only on a clinical but also on a mechanistic level. For a long time, the molecular mechanisms of asthma were considered to be driven by type 2 helper T cells (Th2) and eosinophilic airway inflammation; however, extensive research has revealed that T2-low subtypes that differ from the dominant T2 paradigm are also common.

RECENT FINDINGS

Research into asthma pathways has led to the recognition that some asthma phenotypes show absence of T2 inflammation or alternate between T2 and non-T2 responses. Moreover, numerous immune response modifiers that block key-molecules such as interleukin (IL)-5, IL-13, and immunoglobulin E (IgE) have been identified. Along the way, these studies pointed that T2-low inflammation may also be responsible for lack of responsiveness to current treatment regimes.

SUMMARY

Asthma pathogenesis is characterized by two major endotypes, a T2-high featuring increased eosinophilic airway inflammation, and a T2-low endotype presenting with either neutrophilic or paucigranulocytic airway inflammation and showing greater resistance to steroids. This clearly presents an unmet therapeutic challenge. A precise definition and characterization of the mechanisms that drive this T2-low inflammatory response in each patient phenotype is necessary to help identify novel drug targets and design more effective and targeted treatments.

Blood Eosinophils as Biomarkers to Drive Treatment Choices in Asthma and COPD

BACKGROUND

Asthma and COPD are complex, heterogeneous conditions comprising a wide range of phenotypes, some of which are refractory to currently available treatments. Elucidation of these phenotypes and identification of biomarkers with which to recognize them and guide appropriate treatment remain a priority.

OBJECTIVE

This review describes the utility of blood eosinophils as a surrogate biomarker of eosinophilic airway inflammation, a common feature of specific asthma and COPD phenotypes. The role of blood eosinophils in airway disease is described, as is their relevance in reflecting airway eosinophilia. Each disease is discussed separately as the manner in which blood eosinophils might be used as biomarkers differs. Focusing on patients with severe disease (persistent eosinophilic asthma and exacerbating COPD), we evaluate evidence examining eosinophils as biomarkers.

RESULTS

In asthma, the rationale for using blood eosinophils to guide treatment is clearly defined, backed by prospective, well-controlled studies. Higher eosinophil counts identify patients with more severe disease and poorer outcomes, patients for whom biologic therapies targeting allergic and/or eosinophilic pathways are recommended. In COPD, the evidence is less robust. High blood eosinophil counts are a modest predictor of future exacerbations, and may predict a favourable response to ICS on top of LABA/LAMA, especially in patients with a history of frequent exacerbations.

CONCLUSION

Before extensive application in clinical practice, further evaluation of these findings in prospective clinical studies, and standardization of the appropriate thresholds of clinically relevant eosinophilia are needed, together with establishing whether single or multiple measurements are required in different clinical settings.

Guiding principles for use of newer biologics and bronchial thermoplasty for patients with severe asthma

BACKGROUND

Severe asthma poses significant disease-related and economic burdens in the United States. Challenges in practice include how to define "severe asthma" for a given patient, knowing which are the right tests to perform and when, and having a better understanding of a patient's asthma phenotype. Furthermore, current guidelines do not address a clear, practical approach to treatment that is based on a patient's asthma phenotype.

OBJECTIVE

To develop a consensus on the definition of severe asthma, the role of biomarkers and phenotyping severe asthma, and the use of newer biologic therapies and bronchial thermoplasty to help guide practicing clinicians.

METHODS

A roundtable meeting was convened with a panel of severe asthma experts to discuss areas in practice that are not adequately addressed by current guidelines, specifically phenotype-guided treatment.

RESULTS

We describe a consensus on the definition of severe asthma, asthma phenotyping with the use of available biomarkers, and guiding principles for newer biologic therapies and bronchial thermoplasty.

CONCLUSION

To optimize therapy and improve outcomes such as daily symptoms, quality of life, exacerbations, and hospitalizations, a clear picture of a patient's asthma phenotype is needed to guide therapy. Determining asthma phenotypes is the foundation of precision medicine for this persistent, often difficult-to-treat disease.

Interleukin-5 Inhibitors for Severe Asthma: Rationale and Future Outlook

In this review, we outline the pathophysiology of severe asthma and discuss the role of anti-interleukin (IL)-5 inhibitors for the treatment of asthma. Anti-IL-5 treatments have shown efficacy in reducing the rate of severe asthma attacks in eosinophilic asthma. We review the history of the development of these agents, lessons learnt about severe asthma along the way and key clinical trials supporting efficacy of the three anti-IL-5 treatments that are clinically available or undergoing clinical trials in asthma.