Methods used in clinical development of novel anti-asthma therapies

Targeting key proximal drivers of type 2 inflammation in disease

Systemic type 2 inflammation encompassing T helper 2 (TH2)-type responses is emerging as a unifying feature of both classically defined allergic diseases, such as asthma, and a range of other inflammatory diseases. Rather than reducing inflammation with broad-acting immunosuppressants or narrowly targeting downstream products of the TH2 pathway, such as immunoglobulin E (IgE), efforts to target the key proximal type 2 cytokines - interleukin-4 (IL-4), IL-5 and IL-13 - represent a promising strategy to achieve therapeutic benefit across multiple diseases. After several initial disappointing clinical results with therapies targeting IL-4, IL-5 or IL-13 in asthma, applying a personalized approach achieved therapeutic benefit in an asthma subtype exhibiting an 'allergic' phenotype. More recently, efficacy was extended into a broad population of people with asthma. This argues that the Type 2 inflammation is broadly relevant across the severe asthma population if the key upstream drivers are properly blocked. Moreover, the simultaneous inhibition of IL-4 and IL-13 has shown significant clinical activity in diseases that are often co-morbid with asthma - atopic dermatitis and chronic sinusitis with nasal polyps - supporting the hypothesis that targeting a central 'driver pathway' could benefit multiple allergic diseases.

Advances in asthma drug discovery: evaluating the potential of nasal cell sampling and beyond

INTRODUCTION

Inhaled corticosteroid anti-inflammatory therapy is effective at controlling disease symptoms of asthma, but a subset of patients remains symptomatic despite optimal treatment, creating a clear unmet medical need. Moreover, none of the currently available drugs for asthma are really disease-modifying or curative. Although murine models of asthma, based on transgenic and knockout animals, may offer an integrated pathophysiological system for studying the characteristics of airway inflammation and hyperresponsiveness, these alterations are noteworthily different compared with those observed in asthmatic patients. Since a clear functional and inflammatory relationship between the nasal mucosa and bronchial tissue in patients suffering from asthma and allergic rhinitis has been recognized, using preclinical models based on human nasal cells sampling might support a prompt and effective anti-inflammatory drug discovery in asthma.

AREAS COVERED

The authors provide a review, which discusses the potential role of nasal cell sampling and its application in advanced drug discovery for asthma. The contents range from the similarities and differences between asthma and allergic rhinitis up to artificial airway models based on sophisticated human lung-on-a-chip devices.

EXPERT OPINION

Nasal cell sampling and processing have reached a great potential in asthma drug discovery. The authors believe that models of asthma, which are based on human nasal cells, can provide valuable indications of proof of pharmacological and potential therapeutic efficacy in both preclinical and early clinical settings.

Inhaled allergen bronchoprovocation tests

The allergen bronchoprovocation test is a long-standing exacerbation model of allergic asthma that can induce several clinical and pathophysiologic features of asthma in sensitized subjects. Standardized allergen challenge is primarily a research tool, and when properly conducted by qualified and experienced investigators, it is safe and highly reproducible. In combination with validated airway sampling and sensitive detection techniques, allergen challenge allows the study of several features of the physiology of mainly TH2 cell-driven asthma in relation to the kinetics of the underlying airway pathology occurring during the allergen-induced late response. Furthermore, given the small within-subject variability in allergen-induced airway responses, allergen challenge offers an adequate disease model for the evaluation of new (targeted) controller therapies for asthma in a limited number of subjects. In proof-of-efficacy studies thus far, allergen challenge showed a fair positive predicted value and an excellent negative predictive value for the actual clinical efficacy of new antiasthma therapies, underscoring its important role in early drug development. In this review we provide recommendations on challenge methods, response measurements, sample size, safety, and harmonization for future applications.

Biomarkers in asthma and allergic rhinitis

A biological marker (biomarker) is a physical sign or laboratory measurement that can serve as an indicator of biological or pathophysiological processes or as a response to a therapeutic intervention. An applicable biomarker possesses the characteristics of clinical relevance (sensitivity and specificity for the disease) and is responsive to treatment effects, in combination with simplicity, reliability and repeatability of the sampling technique. Presently, there are several biomarkers for asthma and allergic rhinitis that can be obtained by non-invasive or semi-invasive airway sampling methods meeting at least some of these criteria. In clinical practice, such biomarkers can provide complementary information to conventional disease markers, including clinical signs, spirometry and PC(20)methacholine or histamine. Consequently, biomarkers can aid to establish the diagnosis, in staging and monitoring of the disease activity/progression or in predicting or monitoring of a treatment response. Especially in (young) children, reliable, non-invasive biomarkers would be valuable. Apart from diagnostic purposes, biomarkers can also be used as (surrogate) markers to predict a (novel) drug's efficacy in target populations. Therefore, biomarkers are increasingly applied in early drug development. When implementing biomarkers in clinical practice or trials of asthma and allergic rhinitis, it is important to consider the heterogeneous nature of the inflammatory response which should direct the selection of adequate biomarkers. Some biomarker sampling techniques await further development and/or validation, and should therefore be applied as a "back up" of established biomarkers or methods. In addition, some biomarkers or sampling techniques are less suitable for (very young) children. Hence, on a case by case basis, a decision needs to be made what biomarker is adequate for the target population or purpose pursued. Future development of more sophisticated sampling methods and quantification techniques, such as--omics and biomedical imaging, will enable detection of adequate biomarkers for both clinical and research applications.

Sputum induction with hypertonic saline reduces fractional exhaled nitric oxide in chronic smokers and non-smokers

BACKGROUND

Nitric oxide (NO) measurements in exhaled air and hypertonic saline-induced sputum are commonly used biomarker sampling methods of the lower airways. Both sampling methods have been validated in asthmatic patients and healthy controls, however, data from chronic smokers are scarce.

OBJECTIVES

To evaluate the reproducibility and differences in fractional exhaled NO (FeNO) values in asymptomatic chronic smokers and healthy, non-smoking controls. Furthermore, to test the effect of hypertonic saline sputum induction (SI) on FeNO levels in both study groups.

METHODS

16 asymptomatic chronic smokers and 16 non-smokers participated in this study. Baseline FeNO and forced expiratory volume in 1 s (FEV(1)) were recorded pre- and 30 min post NaCl 4.5% SI (3 x 5 min) on 2 study days (+/-2 h; 4-10 days apart). Mixed ANOVA was used to estimate the intra-subject Coefficient of Variation (CV) % over days; changes in FeNO and FEV(1) values before and after SI, were analyzed by a Student's paired t-test.The difference between smokers and non-smokers was estimated by a Student's t-test.

RESULTS

On day 1, FeNO values in smokers were significantly lower than in non-smokers, 10.6 ppb, and 18.4 ppb, respectively, (42% difference, p = 0.0028, 95% CI: -59%, -19%). In both study groups, FeNO measurements were reproducible, with an intra-subject CV of 27.2% and 19.2%, for smokers and non-smokers, respectively. SI significantly decreased FeNO levels in both study groups on day 1. In smokers, there was a mean reduction in FeNO of almost 37% (p = 0.0045, 95% CI: -53%, -14%), and in non-smokers a mean decrease of almost 37% (95% CI : -53%, -14%; p = 0.0045). In both study groups SI did not affect FEV(1) (p > 0.94).

CONCLUSIONS

Our data extend previous findings in asthmatics and healthy controls to asymptomatic chronic smokers: 1. FeNO measurements are reproducible in both smokers and non-smokers; 2. baseline FeNO levels in chronic smokers are lower than in non-smokers and 3. sputum induction by hypertonic saline reduces FeNO levels in both study groups, without affecting lung function.