Heterogeneity of response to asthma controller therapy: clinical implications

Using a Mixture-of-Bivariate-Regressions Model to Explore Heterogeneity of Effects of the Use of Inhaled Corticosteroids on Gestational Age and Birth Weight Among Pregnant Women With Asthma

Asthma is a heterogeneous disease, and responses to asthma medications vary noticeably among patients. A substantively oriented objective of this study was to explore the potentially heterogeneous effects of exposure to maternal inhaled corticosteroids (ICS) on gestational age (GA) at delivery and birth weight (BW) using a cohort of 6,197 pregnancies among women with asthma (Quebec, Canada, 1998-2008). A methodologically oriented objective was to comprehensively describe the application of a Bayesian 2-component mixture-of-bivariate-regressions model to address this issue and estimate the effects of ICS on GA and BW jointly. Based on the proposed model, no association between ICS and GA/BW was found for a large proportion of asthmatic pregnancies. However, a positive association between ICS exposure and GA/BW was revealed in a small subset of pregnancies comprising mainly preterm and low-birth-weight infants. A novel application of this model was also subsequently performed using BW z score instead of BW as the outcome variable. In conclusion, the studied mixture-of-bivariate-regressions model was useful for detecting heterogeneity in the effect of ICS on GA and BW in our population of women with asthma. These analyses pave the way for analogous uses of this model for general assessment of exposure effect heterogeneity for these perinatal outcomes.

A Bayesian finite mixture of bivariate regression model for causal mediation analyses

Building on the work of Schwartz et al, Joint Bayesian analysis of birthweight and censored gestational age using finite mixture models in Statistics in Medicine, we propose a Bayesian finite mixture of bivariate regression model for causal mediation analyses. Using an identifiability condition within each component of the mixture, we express the natural direct and indirect effects of the exposure on the outcome as functions of the component-specific regression coefficients. On the basis of simulated data, we examine the behavior of the model for estimating these effects in situations where the associations between exposure, mediator, and outcome are confounded or not. Additionally, we demonstrate that this mixture model can be used to account for heterogeneity arising through unmeasured binary or categorical mediator-outcome confounders. Considering gestational age as a potential mediator, we then illustrate our mediation mixture model to estimate the natural direct and indirect effects of exposure to inhaled corticosteroids during pregnancy on birthweight using a cohort of asthmatic women from the province of Quebec (Canada).

Rationale and design of the multiethnic Pharmacogenomics in Childhood Asthma consortium

AIM

International collaboration is needed to enable large-scale pharmacogenomics studies in childhood asthma. Here, we describe the design of the Pharmacogenomics in Childhood Asthma (PiCA) consortium.

MATERIALS & METHODS

Investigators of each study participating in PiCA provided data on the study characteristics by answering an online questionnaire.

RESULTS

A total of 21 studies, including 14,227 children/young persons (58% male), from 12 different countries are currently enrolled in the PiCA consortium. Fifty six percent of the patients are Caucasians. In total, 7619 were inhaled corticosteroid users. Among patients from 13 studies with available data on asthma exacerbations, a third reported exacerbations despite inhaled corticosteroid use. In the future pharmacogenomics studies within the consortium, the pharmacogenomics analyses will be performed separately in each center and the results will be meta-analyzed.

CONCLUSION

PiCA is a valuable platform to perform pharmacogenetics studies within a multiethnic pediatric asthma population.

Cluster analysis of sputum cytokine-high profiles reveals diversity in T(h)2-high asthma patients

Background

Asthma is characterized by a heterogeneous inflammatory profile and can be subdivided into T(h)2-high and T(h)2-low airway inflammation. Profiling of a broader panel of airway cytokines in large unselected patient cohorts is lacking.

Methods

Patients (n = 205) were defined as being “cytokine-low/high” if sputum mRNA expression of a particular cytokine was outside the respective 10^th/90^th percentile range of the control group (n = 80). Unsupervised hierarchical clustering was used to determine clusters based on sputum cytokine profiles.

Results

Half of patients (n = 108; 52.6%) had a classical T(h)2-high (“IL-4-, IL-5- and/or IL-13-high”) sputum cytokine profile. Unsupervised cluster analysis revealed 5 clusters. Patients with an “IL-4- and/or IL-13-high” pattern surprisingly did not cluster but were equally distributed among the 5 clusters. Patients with an “IL-5-, IL-17A-/F- and IL-25- high” profile were restricted to cluster 1 (n = 24) with increased sputum eosinophil as well as neutrophil counts and poor lung function parameters at baseline and 2 years later. Four other clusters were identified: “IL-5-high or IL-10-high” (n = 16), “IL-6-high” (n = 8), “IL-22-high” (n = 25). Cluster 5 (n = 132) consists of patients without “cytokine-high” pattern or patients with only high IL-4 and/or IL-13.

Conclusion

We identified 5 unique asthma molecular phenotypes by biological clustering. Type 2 cytokines cluster with non-type 2 cytokines in 4 out of 5 clusters. Unsupervised analysis thus not supports a priori type 2 versus non-type 2 molecular phenotypes. www.clinicaltrials.gov NCT01224938. Registered 18 October 2010.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-017-0524-y) contains supplementary material, which is available to authorized users.

Therapeutic novelties of inhaled corticosteroids and bronchodilators in asthma

Orally inhaled agents are a key therapeutic class for treatment of asthma. Inhaled corticosteroids (ICS) are the most effective anti-inflammatory treatment for asthma thus representing the first-line therapy and bronchodilators complement the effects of ICSs. A significant body of evidence indicates that addition of a β2-agonist to ICS therapy is more effective than increasing the dose of ICS monotherapy. In this paper, pharmacological features of available ICSs and bronchodilators will be reviewed with a focus on fluticasone propionate/formoterol fumarate combination which represents the one of the most powerful ICS acting together with the most rapid active LABA.

Heterogeneity of response to therapy

As noted in prior chapters, US national and international guidelines provide a consistent approach to initial management of asthma, based on easily observed physical and physiologic findings, and a detailed history. From those data, a rational initial therapeutic regimen can be prescribed. In many cases, such therapy results in near complete control of asthma symptoms, restoration of normal lung physiology, and elimination of exacerbations. In fact, such improvement is frequent enough that therapeutic responsiveness to asthma treatments was thought to be nearly universal. However, it is not uncommon for patients to return with incomplete, or even trivial improvement in these clinical metrics of control (Langmack and Martin Curr Opin Pulm Med 16:13-18, 2010). In this chapter, we review the current literature on the variability of response to commonly used therapeutic agents in asthma.

Impact of montelukast on asthma associated with rhinitis, and other triggers and co-morbidities

INTRODUCTION

Rhinitis and other specific triggers or co-morbidities (tobacco exposure, excess weight, aspirin sensitivity or heredity factors) are frequently associated with uncontrolled asthma. Asthma associated with these exacerbating factors appears to be related to an increase in leukotriene-mediated inflammation.

METHODS

We reviewed the role of montelukast, a leukotriene receptor antagonist, in the treatment of asthma associated with these factors by using the PubMed database to search the English and French biomedical literature for articles describing randomized-controlled trials, large observational studies and reviews (published up to May 2012, inclusive).

RESULTS

Montelukast, either alone or in combination with other drugs, is an effective treatment against rhinitis-associated asthma. Montelukast also offers therapeutic benefits against exercise-induced asthma or in cases of asthma linked to tobacco exposure, excess weight or aspirin hypersensitivity. Thus, for some patients, montelukast may constitute an alternative to the gold-standard treatment of inhaled corticosteroids. Polymorphisms in several genes encoding proteins of the leukotriene signaling pathway may contribute to the variability in response to montelukast.

CONCLUSIONS

In conclusion, we have shown that montelukast treatment could be of particular benefit to subgroups of patients with asthma associated with rhinitis, exercise, tobacco exposure, being overweight or aspirin hypersensitivity.

Inhaled corticosteroid and long-acting β2-agonist pharmacological profiles: effective asthma therapy in practice

Fixed-dose combinations of inhaled corticosteroids (ICSs) and long-acting β2-agonists (LABAs) have been used to manage asthma for several years. They are the preferred therapy option for patients who do not achieve optimal control of their asthma with low-dose ICS monotherapy. In Europe, four ICS/LABA products are commercially available for asthma maintenance therapy (fluticasone propionate/formoterol fumarate, fluticasone propionate/salmeterol xinafoate, budesonide/formoterol fumarate and beclometasone dipropionate/formoterol fumarate), and other combinations are likely to be developed over the next few years (e.g. mometasone/formoterol fumarate, fluticasone furoate/vilanterol, mometasone/indacaterol). Data from randomized, controlled, clinical trials do not demonstrate a clear overall efficacy difference among ICS/LABA combinations approved for asthma therapy. Conversely, pharmacological data indicate that there may be certain advantages to using one ICS or LABA over another because of the specific pharmacodynamic and pharmacokinetic profiles associated with particular treatments. This review article summarizes the pharmacological characteristics oft he various ICSs and LABAs available for the treatment of asthma, including the potential for ICS and LABA synergy, and gives an insight into the rationale for the development of the latest ICS/LABA combination approved for asthma maintenance therapy.

[Montelukast in the treatment of mild to moderate persistent asthma]

INTRODUCTION

Anti-inflammatory preventive treatment is recommended in cases of persistent asthma. Besides inhaled corticosteroids (ICS), which represent the mainstay of treatment, other therapeutic options are available, of which only antileukotrienes are approved for all age groups.

BACKGROUND

Given as a substitute of low-dose ICS, montelukast prevents exacerbations as efficiently and for a longer period than long-acting β2-agonists. Montelukast is as efficient as doubling the dose of ICS on asthma symptoms in cases of inadequate control with low-dose ICS. Combined with ICS, it can lead to better control of asthma and potentially to ICS sparing.

CONCLUSIONS

Given the efficacy, tolerance and long-term treatment compliance of montelukast in mild persistent asthma in adults and children, montelukast, given as a substitute or combined with ICS, could contribute to enhanced control of asthma, especially in children.

Impact of asthma controller medications on medical and economic resource utilization in adult asthma patients

OBJECTIVE

To compare asthma-related resource utilization, adherence and costs among adults prescribed asthma controller regimens.

RESEARCH DESIGN AND METHODS

Medical and pharmacy claims from a US managed-care claims database were used to identify adults (18-56 years) initiating asthma controller therapy. Patients had 2 years continuous enrollment and ≥ 1 medical claims for asthma (ICD9: 493.xx) (January 2004 - March 2009). Asthma exacerbations, short-acting β-agonist (SABA) fills, adherence (MPR ≥ 0.80) and asthma-related costs were assessed for 1 year after the initial asthma controller medication claim. Separate logistic and negative binomial regression models for monotherapy and combination therapy were developed to examine the impact of controller therapy on outcomes.

RESULTS

A total of 28 074 patients [inhaled corticosteroids (ICS) (26.3%), leukotriene modifiers (LM) (23.2%), ICS  +  long acting β-agonist (LABA) (48.5%), ICS + LM (2%)] were included. LM patients had lower odds of ≥ 6 SABA fills (OR(adj) = 0.83, 95% CI: 0.73-0.96) and lower rates of asthma exacerbations (RR(adj) = 0.82, 0.75-0.89) vs. ICS patients. Odds of ≥ 6 SABA fills were similar for ICS + LM vs. ICS + LABA (OR(adj) = 1.3, 0.96-1.76); the rate of asthma exacerbations was greater for ICS + LM compared with ICS + LABA (OR(adj) = 1.4, 1.2-1.6). The proportion adherent was greatest for LM (14.9%) and ICS + LABA (4.1%). LM patients had higher unadjusted pharmacy costs, but lower medical costs compared to ICS patients. For combination therapy, ICS + LM had higher unadjusted mean medical and pharmacy costs vs. ICS + LABA. Higher adjusted mean total costs in the post-index period were observed for LM vs. ICS patients ($837 vs. 684) and for ICS + LM vs. ICS + LABA patients ($1223 vs. 873).

CONCLUSIONS

LM monotherapy was associated with lower medical costs but higher total costs resulting from greater treatment adherence. Conversely, higher costs for ICS + LM resulted from greater exacerbations compared to ICS + LABA despite similar adherence. Higher total costs with LM were due to drug costs. Precise utilization of the medications filled by patients could not be determined.

Recent advances in antileukotriene therapy

PURPOSE OF REVIEW

Despite profound effects of leukotrienes in experimental models, clinical responses to antileukotriene drugs are highly heterogeneous. This review discusses recent advances concerning the molecular mechanisms of antileukotrienes as well as their efficacy in various clinical scenarios and patient groups.

RECENT FINDINGS

Appreciation of the role of leukotriene E4 and the existence of its distinct receptors may explain the limited efficacy of current leukotriene receptor antagonists. Pharmacogenetic studies highlight the influence of several leukotriene pathway genes on clinical responsiveness. Benefits of addition of antileukotrienes to inhaled corticosteroids in chronic adult asthmatics have been shown, but their role in acute asthma is unclear. Evidence suggests they are not a first-line treatment for allergic rhinitis or urticaria, but may provide useful additional therapy. In children antileukotrienes provide symptomatic benefit in preschool wheezers, but have no clear role in bronchiolitis or acute asthma. Adherence to montelukast appears superior to inhaled corticosteroids. Use in sleep-disordered breathing and eosinophilic gastroenteropathies warrants further investigation. Despite recent concerns thorough analysis of existing data suggests antileukotrienes are well tolerated drugs. The possible link with Churg-Strauss syndrome requires further investigation.

SUMMARY

The leukotriene pathway remains an attractive target in asthma and allergic disease, particularly in light of renewed appreciation of the role of leukotriene E4. Clarification of the clinical role of antileukotrienes is needed.