Bronchial thermoplasty in asthma: current perspectives

A dynamical model of TGF-β activation in asthmatic airways

Excessive activation of the regulatory cytokine transforming growth factor $\beta $ (TGF-$\beta $) via contraction of airway smooth muscle (ASM) is associated with the development of asthma. In this study, we develop an ordinary differential equation model that describes the change in density of the key airway wall constituents, ASM and extracellular matrix (ECM), and their interplay with subcellular signalling pathways leading to the activation of TGF-$\beta $. We identify bistable parameter regimes where there are two positive steady states, corresponding to either reduced or elevated TGF-$\beta $ concentration, with the latter leading additionally to increased ASM and ECM density. We associate the former with a healthy homeostatic state and the latter with a diseased (asthmatic) state. We demonstrate that external stimuli, inducing TGF-$\beta $ activation via ASM contraction (mimicking an asthmatic exacerbation), can perturb the system irreversibly from the healthy state to the diseased one. We show that the properties of the stimuli, such as their frequency or strength, and the clearance of surplus active TGF-$\beta $, are important in determining the long-term dynamics and the development of disease. Finally, we demonstrate the utility of this model in investigating temporal responses to bronchial thermoplasty, a therapeutic intervention in which ASM is ablated by applying thermal energy to the airway wall. The model predicts the parameter-dependent threshold damage required to obtain irreversible reduction in ASM content, suggesting that certain asthma phenotypes are more likely to benefit from this intervention.

Effective viral-mediated lung gene therapy: is airway surface preparation necessary?

Gene-based therapeutics are actively being pursued for the treatment of lung diseases. While promising advances have been made over the last decades, the absence of clinically available lung-directed genetic therapies highlights the difficulties associated with this effort. Largely, progress has been hindered by the presence of inherent physical and physiological airway barriers that significantly reduce the efficacy of gene transfer. These barriers include surface mucus, mucociliary action, cell-to-cell tight junctions, and the basolateral cell membrane location of viral receptors for many commonly used gene vectors. Accordingly, airway surface preparation methods have been developed to disrupt these barriers, creating a more conducive environment for gene uptake into the target airway cells. The two major approaches have been chemical and physical methods. Both have proven effective for increasing viral-mediated gene transfer pre-clinically, although with variable effect depending on the specific strategy employed. While such methods have been explored extensively in experimental settings, they have not been used clinically. This review covers the airway surface preparation strategies reported in the literature, the advantages and disadvantages of each method, as well as a discussion about applying this concept in the clinic.

Overview of severe asthma, with emphasis on pediatric patients: a review for practitioners

Asthma is the most common life-threatening chronic disease in children. Although guidelines exist for the diagnosis and treatment of asthma, treatment of severe, pediatric asthma remains difficult. Limited studies in the pediatric population on new asthma therapies, complex issues with adolescence and adherence, health disparities, and unequal access to guideline-based care complicate the care of children with severe, persistent asthma. The purpose of this review is to provide an overview of asthma, including asthma subtypes, comorbidities, and risk factors, to discuss diagnostic considerations and pitfalls and existing treatments, and then present existing and emerging therapeutic approaches to asthma management. An improved understanding of asthma heterogeneity, clinical characteristics, inflammatory patterns, and pathobiology can help further guide the management of severe asthma in children. More studies are needed in the pediatric population to understand emerging therapeutics application in children. Effective multimodal strategies tailored to individual characteristics and a commitment to address risk factors, modifiers, and health disparities may help reduce the burden of asthma in the USA.

Drug Repurposing: The Anthelmintics Niclosamide and Nitazoxanide Are Potent TMEM16A Antagonists That Fully Bronchodilate Airways

There is an unmet need in severe asthma where approximately 40% of patients exhibit poor β-agonist responsiveness, suffer daily symptoms and show frequent exacerbations. Antagonists of the Ca2+-activated Cl- channel, TMEM16A, offers a new mechanism to bronchodilate airways and block the multiple contractiles operating in severe disease. To identify TMEM16A antagonists we screened a library of ∼580,000 compounds. The anthelmintics niclosamide, nitazoxanide, and related compounds were identified as potent TMEM16A antagonists that blocked airway smooth muscle depolarization and contraction. To evaluate whether TMEM16A antagonists resist use- and inflammatory-desensitization pathways limiting β-agonist action, we tested their efficacy under harsh conditions using maximally contracted airways or airways pretreated with a cytokine cocktail. Stunningly, TMEM16A antagonists fully bronchodilated airways, while the β-agonist isoproterenol showed only partial effects. Thus, antagonists of TMEM16A and repositioning of niclosamide and nitazoxanide represent an important additional treatment for patients with severe asthma and COPD that is poorly controlled with existing therapies. It is of note that drug repurposing has also attracted wide interest in niclosamide and nitazoxanide as a new treatment for cancer and infectious disease. For the first time we identify TMEM16A as a molecular target for these drugs and thus provide fresh insights into their mechanism for the treatment of these disorders in addition to respiratory disease.

Effectiveness and Safety of Bronchial Thermoplasty in Severe Asthma in Clinical Practice in Spain

Background

Bronchial thermoplasty (BT) is a minimally invasive procedure consisting of application of thermal energy into the airways to produce ablation of the hypertrophic smooth muscle. It was approved for use in moderate-severe asthma in Spain in 2010.

Objectives

The aims of the present study are to analyze the effectiveness and the safety of BT in clinical practice in our center.

Methods

Participants had a confirmed diagnosis of severe asthma and poor control without therapeutic alternative. Effectiveness was measured by comparing exacerbations, admissions rates, asthma control, and medication 1 year prior and 1 year after BT was completed. All complications appearing during the procedure and in the first year were recorded.

Results

Patients had a mean age of 51 (SD 8) years and were predominantly female (17/23). The average number of activations per patient was 147 (16). The number of severe exacerbations was reduced by 75% (p < 0.001). A 38% reduction in admissions per year was also observed (p = 0.03). The Asthma Control Test improved by 7.1 (3.7) points (p = 0.018). Before BT, the dose of inhaled corticosteroids was 1,621 (1,015) µg of budesonide-equivalent and the dose of oral corticosteroids was 15 (13) mg of prednisone-equivalent. There was a reduction in 430 (731) µg of budesonide-equivalent (p = 0.02) and 4 (11) mg of prednisone (p = 0.094). No changes in lung function were observed. Complications were related mostly to exacerbation of asthma in the days following the procedure.

Conclusions

BT is effective and safe for severe uncontrolled bronchial asthma in real clinical practice.

Non-eosinophilic asthma: current perspectives

Although non-eosinophilic asthma (NEA) is not the best known and most prevalent asthma phenotype, its importance cannot be underestimated. NEA is characterized by airway inflammation with the absence of eosinophils, subsequent to activation of non-predominant type 2 immunologic pathways. This phenotype, which possibly includes several not well-defined subphenotypes, is defined by an eosinophil count <2% in sputum. NEA has been associated with environmental and/or host factors, such as smoking cigarettes, pollution, work-related agents, infections, and obesity. These risk factors, alone or in conjunction, can activate specific cellular and molecular pathways leading to non-type 2 inflammation. The most relevant clinical trait of NEA is its poor response to standard asthma treatments, especially to inhaled corticosteroids, leading to a higher severity of disease and to difficult-to-control asthma. Indeed, NEA constitutes about 50% of severe asthma cases. Since most current and forthcoming biologic therapies specifically target type 2 asthma phenotypes, such as uncontrolled severe eosinophilic or allergic asthma, there is a dramatic lack of effective treatments for uncontrolled non-type 2 asthma. Research efforts are now focusing on elucidating the phenotypes underlying the non-type 2 asthma, and several studies are being conducted with new drugs and biologics aiming to develop effective strategies for this type of asthma, and various immunologic pathways are being scrutinized to optimize efficacy and to abolish possible adverse effects.

Utility of a thin bronchoscope in facilitating bronchial thermoplasty

Background

A significant correlation has been previously demonstrated between the quantum of radiofrequency treatment delivered at bronchial thermoplasty and the degree of improvement in an asthmatic patient’s symptoms. The standard bronchoscope used for bronchial thermoplasty has an outer diameter of 4.8 mm at the distal tip. Thinner bronchoscopes are now available with the same internal channel size (2.0 mm). This study assesses whether using a thinner bronchoscope facilitates bronchial thermoplasty by increasing the radiofrequency activations delivered.

Patients and methods

This was a sequential study in a single center, conducted in 27 patients with very severe asthma. The first 12 patients (Group 1) underwent bronchial thermoplasty using the standard bronchoscope, Olympus BF-Q190. In the next group of eight patients (Group 2), the standard bronchoscope was used for all procedures except the left upper lobe, while the left upper lobe was treated with a smaller bronchoscope, Olympus BF-P190, with an outer diameter of 4.2 mm. In the last group of seven patients (Group 3), the smaller bronchoscope was used for every lobe. The quantum of radiofrequency treatment was measured by activations delivered to each lung lobe in each patient, and patient groups were compared by ANOVA.

Results

In this group of 27 patients, the mean age was 56.5±12.9 years, the mean Asthma Control Questionnaire-5 item version score was 3.2±1.0 and the mean FEV₁% predicted was 55.2±15.7. Bronchial thermoplasty treatment resulted in significant improvements in predicted Asthma Control Questionnaire-5 item version score (to 1.8±1.3, P<0.005), salbutamol rescue usage and oral corticosteroid requiring exacerbations, with no significant change in lung function. Use of the smaller bronchoscope resulted in greater radiofrequency treatment (total activations Group 1: 155±21, Group 2: 176±46, Group 3: 213±37; P<0.01). There were no significant differences in efficacy or safety outcomes among groups.

Conclusion

Using a thinner bronchoscope facilitates access to the bronchial tree and increases the radiofrequency treatment delivered at bronchial thermoplasty.

Asthma Phenotypes and Endotypes: Implications for Personalised Therapy

Asthma is increasingly recognised as a heterogeneous group of diseases with similar clinical presentations rather than a singular disease entity. Asthma was historically categorised by clinical symptoms; however, newer methods of subgrouping, describing and categorising the disease have sub-defined asthma. These sub-definitions are intermittently called phenotypes or endotypes, but the real meanings of these words are poorly understood. Novel treatments are currently and increasingly available, partly in the monoclonal antibody environment, and also some physical therapies (bronchial thermoplasty), but additionally small molecules are not far away from clinical practice. Understanding the disease pathogenesis and the mechanism of action more completely may enable identification of treatable traits, biomarkers, mediators and modifiable therapeutic targets. However, there remains a danger that clinicians become preoccupied with the concept of endotypes and biomarkers, ignoring therapies that are hugely effective but have no companion biomarker. This review discusses our understanding of the concept of phenotypes and endotypes in appreciating and managing the heterogeneous condition that is asthma. We consider the role of functional imaging, physiology, blood-, sputum- and breath-based biomarkers and clinical manifestations that could be used to produce a personalised asthma profile, with implications on prognosis, pathophysiology and most importantly specific therapeutic responses. With the advent of increasing numbers of biological therapies and other interventional options such as bronchial thermoplasty, the importance of targeting expensive therapies to patients with the best chance of clinical response has huge health economic importance.

In vitro, in silico and in vivo study challenges the impact of bronchial thermoplasty on acute airway smooth muscle mass loss

Bronchial thermoplasty is a treatment for asthma. It is currently unclear whether its histopathological impact is sufficiently explained by the proportion of airway wall that is exposed to temperatures necessary to affect cell survival.

Airway smooth muscle and bronchial epithelial cells were exposed to media (37–70°C) for 10 s to mimic thermoplasty. In silico we developed a mathematical model of airway heat distribution post-thermoplasty. In vivo we determined airway smooth muscle mass and epithelial integrity pre- and post-thermoplasty in 14 patients with severe asthma.

In vitro airway smooth muscle and epithelial cell number decreased significantly following the addition of media heated to ≥65°C. In silico simulations showed a heterogeneous heat distribution that was amplified in larger airways, with <10% of the airway wall heated to >60°C in airways with an inner radius of ∼4 mm. In vivo at 6 weeks post-thermoplasty, there was an improvement in asthma control (measured via Asthma Control Questionnaire-6; mean difference 0.7, 95% CI 0.1–1.3; p=0.03), airway smooth muscle mass decreased (absolute median reduction 5%, interquartile range (IQR) 0–10; p=0.03) and epithelial integrity increased (14%, IQR 6–29; p=0.007). Neither of the latter two outcomes was related to improved asthma control.

Integrated in vitro and in silico modelling suggest that the reduction in airway smooth muscle post-thermoplasty cannot be fully explained by acute heating, and nor did this reduction confer a greater improvement in asthma control.

Bronchial thermoplasty treatment for asthma has unexpected possible mechanisms of actionhttp://ow.ly/ZcuE30jsaSa

Bronchial thermoplasty in severe asthma in Australia

BACKGROUND

Bronchial thermoplasty (BT) is an approved bronchoscopic intervention for the treatment of severe asthma. However, limited published experience exists outside of clinical trials regarding patient selection and outcomes achieved.

AIMS

To evaluate the effectiveness and safety of BT in patients with severe asthma encountered in clinical practice.

METHODS

This is a retrospective analysis of the first 'real world' data from Australia. The following outcomes were measured prior to, and 6 months following BT: spirometry, Asthma Control Questionnaire-5 (ACQ-5) score, reliever and preventer medication use and exacerbation history.

RESULTS

Twenty patients were treated from June 2014 to December 2015 at three university teaching hospitals. All subjects met the European Respiratory Society/American Thoracic Society definition of severe asthma. Mean pre-bronchodilator forced expiratory volume in 1 s was 62.8 ± 16.6% predicted (range: 33-95%). All patients were being treated with high dose inhaled corticosteroids, long-acting beta₂ agonists and long-acting muscarinic antagonists. Ten patients (50%) were taking maintenance oral prednisolone. Most subjects also required at least one of montelukast (65%), omalizumab (30%) and methotrexate (20%). ACQ-5 improved from 3.6 ± 1.1 at baseline to 1.6 ± 1.2 at 6 months, P < 0.001. Short-acting reliever use decreased from a median of 8.0-0.25 puffs/day, P < 0.001, and exacerbations requiring corticosteroids also significantly reduced. Five of 10 patients completely discontinued maintenance oral corticosteroids. Ten patients with a baseline forced expiratory volume in 1 s of <60% predicted significantly improved from 49.2 ± 9.6% to 61.8 ± 17.6%, P < 0.05. Only two procedures required hospitalisation beyond the planned overnight admission.

CONCLUSION

BT is a safe procedure which can achieve clinical improvement in those with uncontrolled symptoms and severe airflow obstruction.

Traditional Therapies for Severe Asthma

Severe asthma is a complex and heterogeneous disease. The European Respiratory Society and American Thoracic Society guidelines define severe asthma for patients 6 years or older as "asthma which requires treatment with high-dose inhaled corticosteroids…plus a second controller or systemic corticosteroids to prevent it from becoming 'uncontrolled' or which remains 'uncontrolled' despite this therapy." This article reviews available traditional therapies, data behind their uses in severe asthma, and varying recommendations. As various asthma endotypes and phenotypes are better understood and characterized, targeted therapies should help improve disease outcomes, efficacy, and cost-effectiveness.

Inter-airway structural heterogeneity interacts with dynamic heterogeneity to determine lung function and flow patterns in both asthmatic and control simulated lungs

Asthma is a disease involving both airway remodelling (e.g. thickening of the airway wall) and acute, reversible airway narrowing driven by airway smooth muscle contraction. Both of these processes are known to be heterogeneous, and in this study we consider a new theoretical model which considers the interactions of both mechanisms: structural heterogeneity (variation in airway remodelling) and dynamic heterogeneity (emergent variation in airway narrowing and flow). By integrating both types of inter-airway heterogeneity in a full human lung geometry, we are able to draw several insights regarding the mechanisms underlying observed ventilation heterogeneity. We show that: (1) bimodal ventilation distributions are driven by paradoxical contraction/dilation patterns for airways of all sizes; (2) structural heterogeneity differences between asthmatic and control subjects significantly influences resulting lung function, and observed ventilation heterogeneity patterns; and (3) individual airway dilation probabilities are uncorrelated with prior airway remodelling of that airway.

Emerging interleukin receptor antagonists for the treatment of asthma

INTRODUCTION

Asthma is a heterogeneous disease, usually characterized by chronic airway inflammation. Most patients with asthma can be well-controlled with inhaled corticosteroids and, if necessary, the addition of a long-acting beta agonist. Despite these therapies, 5% to 10% of patients with asthma have severe, uncontrolled asthma. Selecting patients based on peripheral eosinophil counts and a history of exacerbations has led to significant decreases in exacerbations and an improvement in asthma control with medications that target IL-4, IL-5 and IL-13/. Areas covered: This review will cover the definition of severe asthma, existing treatment options, biomarkers, and the emerging role of interleukin antagonists in the treatment of severe asthma. Expert opinion: IL antagonists are novel drugs targeting important inflammatory cytokines in asthma. Anti-IL-5 drugs provide the most promise as they have obtained regulatory approval and are available for use. Anti-IL-4 drug results are also promising. There is, however, uncertainty regarding the success of anti-IL-13 drugs development at this point. An ongoing focus of research is to significantly increase our understanding of the biology of asthma, and in particular severe asthma, making more and better targeted therapies. There may also be potential in the future to use these new drugs earlier in the development of asthma, as disease-modifying interventions that might be associated with remission or even cure.

An Official American Thoracic Society Research Statement: Current Challenges Facing Research and Therapeutic Advances in Airway Remodeling

BACKGROUND

Airway remodeling (AR) is a prominent feature of asthma and other obstructive lung diseases that is minimally affected by current treatments. The goals of this Official American Thoracic Society (ATS) Research Statement are to discuss the scientific, technological, economic, and regulatory issues that deter progress of AR research and development of therapeutics targeting AR and to propose approaches and solutions to these specific problems. This Statement is not intended to provide clinical practice recommendations on any disease in which AR is observed and/or plays a role.

METHODS

An international multidisciplinary group from within academia, industry, and the National Institutes of Health, with expertise in multimodal approaches to the study of airway structure and function, pulmonary research and clinical practice in obstructive lung disease, and drug discovery platforms was invited to participate in one internet-based and one face-to-face meeting to address the above-stated goals. Although the majority of the analysis related to AR was in asthma, AR in other diseases was also discussed and considered in the recommendations. A literature search of PubMed was performed to support conclusions. The search was not a systematic review of the evidence.

RESULTS

Multiple conceptual, logistical, economic, and regulatory deterrents were identified that limit the performance of AR research and impede accelerated, intensive development of AR-focused therapeutics. Complementary solutions that leverage expertise of academia and industry were proposed to address them.

CONCLUSIONS

To date, numerous factors related to the intrinsic difficulty in performing AR research, and economic forces that are disincentives for the pursuit of AR treatments, have thwarted the ability to understand AR pathology and mechanisms and to address it clinically. This ATS Research Statement identifies potential solutions for each of these factors and emphasizes the importance of educating the global research community as to the extent of the problem as a critical first step in developing effective strategies for: (1) increasing the extent and impact of AR research and (2) developing, testing, and ultimately improving drugs targeting AR.