Methacholine challenge tests to demonstrate therapeutic equivalence of terbutaline sulfate via different Turbuhaler® devices in patients with mild to moderate asthma: Appraisal of a four-way crossover design

Allergen Provocation Tests in Respiratory Research: Building on 50 Years of Experience

Allergen provocation test is an established model of allergic airway diseases, including asthma and allergic rhinitis, allowing the study of allergen-induced changes in respiratory physiology and inflammatory mechanisms in sensitised individuals as well as their associations. In the upper airways, allergen challenge is focused on the clinical and pathophysiological sequelae of the early allergic response and applied both as a diagnostic tool and in research settings. In contrast, the bronchial allergen challenge has almost exclusively served as a research tool in specialised research settings with a focus on the late asthmatic response and the underlying type 2 inflammation. The allergen-induced late asthmatic response is also characterised by prolonged airway narrowing, increased non-specific airway hyperresponsiveness and features of airway remodelling including the small airways, and hence, allows the study of several key mechanisms and features of asthma. In line with these characteristics, the allergen challenge has served as a valued tool to study the crosstalk of the upper and lower airways and in proof of mechanism studies of drug development. In recent years, several new insights into respiratory phenotypes and endotypes including the involvement of the upper and small airways, innovative biomarker sampling methods and detection techniques, refined lung function testing as well as targeted treatment options, further shaped the applicability of the allergen provocation test in precision medicine. These topics, along with descriptions of subject populations and safety, in line with the updated GINA2021, will be addressed in this paper.

The use of methacholine provocation when assessing therapeutic equivalence between two inhalers in asthmatic patients

A planned change from Bricanyl® (terbutaline) Turbuhaler® M2 to M3 device required a pharmacodynamic study to evaluate therapeutic equivalence of the two devices. Because of the flat dose-response curve for this type of agent over this dose range when assessing bronchodilation, a bronchoprotection study was considered more feasible. In this double-blind, double-dummy, multicentre, single-dose, two-factor, crossover study, patients with stable mild-to-moderate asthma were randomised to 0.5 or 1.5 mg terbutaline via Turbuhaler® M2 or Turbuhaler® M3 followed by a methacholine challenge test. Primary outcome variable: concentration of methacholine causing a 20% fall in FEV₁ (PC₂₀). Pairwise contrasts were constructed with 95% CIs to determine assay sensitivity for M2 and M3 devices and therapeutic equivalence at each dose level (95% CI for M3:M2 devices within pre-specified limit [0.67-1.50]) and the relative dose-potency (RDP) between M3 and M2 determined with 90% CI. Sixty patients were randomised and all completed the study. Between-device ratios of PC₂₀ (M3:M2) were 0.92 (95% CI: 0.75-1.13) for 0.5 mg and 0.88 (95% CI 0.72-1.08) for 1.5 mg and estimated RDP was 1.20 (0.96-1.53). In conclusion, a methacholine provocation study (PC₂₀ primary variable) is a useful alternative to the standard bronchodilation study when assessing therapeutic equivalence of a bronchodilator.

Enhancement of lung gene delivery after aerosol: a new strategy using non-viral complexes with antibacterial properties

The pathophysiology of obstructive pulmonary diseases, such as cystic fibrosis (CF), leads to the development of chronic infections in the respiratory tract. Thus, the symptomatic management of the disease requires, in particular, repetitive antibiotherapy. Besides these antibacterial treatments, certain pathologies, such as CF or chronic obstructive pulmonary disease (COPD), require the intake of many drugs. This simultaneous absorption may lead to undesirable drug interactions. For example, Orkambi® (lumacaftor/Ivacaftor, Vertex), a pharmacological drug employed to treat F508del patients, cannot be used with antibiotics such as rifampicin or rifabutin (rifamycin family) which are necessary to treat Mycobacteriaceae. As far as gene therapy is concerned, bacteria and/or biofilm in the airways present an additional barrier for gene transfer. Thus, aerosol administration of nanoparticles have to overcome many obstacles before allowing cellular penetration of therapeutic compounds. This review focusses on the development of aerosol formulations adapted to the respiratory tract and its multiple barriers. Then, formulations that are currently used in clinical applications are summarized depending on the active molecule delivered. Finally, we focus on new therapeutic approaches to reduce possible drug interactions by transferring the antibacterial activity to the nanocarrier while ensuring the transfection efficiency.