Small Airways Disease (SAD) in Severe Asthma as a Novel Endpoint and Distinct Target for Biological Therapy.

Study hypothesis We hypothesize that biological therapy has a significant beneficial effect on small airways disease in severe asthmatics and that the evaluation of small airways before and during treatment may represent a distinctive marker of response and a novel target for a preferential use of one over other biological therapies currently available for severe asthmatic patients.

Study objectives

• To evaluate small airway endpoints in severe asthmatics before starting biologic treatment.
• To evaluate longitudinal changes of these endpoints at different time points during biologic treatment.
• To relate small airway endpoints recorded at baseline and their changes over time to other functional, laboratory, clinical and patient-reported outcomes.
• To make comparisons for subgroups identified on the basis of the type of the biological drug used.

Study center

The study will be conducted at the Asthma Center of Fondazione Policlinico Universitario Agostino Gemelli. Asthma Clinic evaluates approximately 1000 asthmatic patients per year; furthermore, it is part of the Italian Severe Asthma Network (SANI) and one of the coordinating centers for the newborn Italian Mild-Moderate Asthma Network (MANI), therefore representing a center of excellence and reference at a national level, with easy and wide access to the study population.

Study design This is a 24-month, single-site observational retrospective and prospective longitudinal cohort study involving asthmatic patients referred to the Asthma Center and eligible for starting one of the biological therapy currently available. The patient will be considered eligible only after having optimized adherence, inhalation technique, comorbidity management and following a multidisciplinary assessment. Subjects will be monitored for 12 months and SA endpoints as well as other functional, clinical, laboratory and patient-reported outcomes will be recorded at the beginning of the biological therapy (T0) and after 3,6,12 months (T3, T6, T12). Values and changes in SA endpoints will be also related to other functional, clinical and patient-reported outcomes.

Study procedures

The following study procedures will be performed in the framework of the standard care for severe asthmatic patients:

• Clinical history;
• Demographics data (such as age, sex, race et.)
• Questionnaires (i.e. Asthma Control Test [ACT], Asthma Control Questionnaire [ACQ], Asthma Quality of Life Questionnaire [AQLQ])
• Pulmonary function tests (i.e. spirometry [Forced Expiratory volume in 1 second (FEV1),Forced Vital Capacity (FVC), FEV1/FVC, body plethysmography [Residual Volume (RV), Total Lung Capacity (TLC), RV/TLC, impulse oscillometry as resistance at 5 and 20 Hz (R5, R20).
• Airway inflammatory markers (i.e. fraction exhaled nitric oxide - FeNO)
• Allergy tests (i.e. skin-prick tests and immunoassays for total and specific serum IgE)
• Biological sampling (i.e. blood and sputum eosinophils).
• Imaging (i.e. chest XR and HRCT)

Study endpoints The primary endpoint will be represented by the R5-R20 parameter registered through impulsoscillometry. Baseline values and changes over the one-year follow-up period at preplanned timepoints (i.e. 3, 6, and 12 months) will be recorded. According to literature evidence, baseline values ≥0.07 support the evidence of small airways dysfunction.

Secondary endpoints will be represented by indirect parameters of SA involvement (i.e. TLC, RV, TLC/RV, FEF25-75). Baseline values and changes over the one-year follow-up period at preplanned timepoints (i.e. 3, 6, and 12 months) will be recorded.

Variations in primary and secondary endpoints will be also related to changes in functional parameters (i.e FEV1), clinical parameters (exacerbation rate), inflammatory markers (FeNO) and patients' questionnaire scores (ACT, AQLQ, ACQ). Established minimal clinically important difference (MCID) thresholds will be taken into consideration for correlation analyses.

Statistical analysis Statistical analysis will be performed using a statistical software. Data will be tested for normality and will be expressed as mean (SD) or median (IQR). Comparative analysis will be performed using parametric and non-parametric methods as appropriate. Single and multiple linear regression analyses will be run to determine correlation between small airway endpoints and clinical, functional, laboratory, and patients' reported outcomes. A p-value≥0.05 will be considered statistically significant. Most appropriate statistical analyses and models will be anyway chosen and run, following the advice of statisticians at the institutional Department of Public Health. Considering the "R5-R20 Delta", measured through impulse oscillometry, as the primary endpoint for the study, and aiming for a minimal difference of 0.02 (according to literature data), in order to have an a error of 0.5 and a study power of 80%, at least 54 subjects will have to be enrolled in the study. Documentation will be stored for a minimum of 10 years after the completion of the study, including the follow-up period.

Study significance and innovation Systems biology approaches are establishing the links between disease pathways/mechanisms, and clinical/physiologic features. Validation of these pathways may contribute to better defining severe asthma endotypes and treatable mechanisms. Precision medicine approaches are necessary to link treatable mechanisms with treatable traits and biomarkers derived from clinical, physiologic, inflammatory, molecular and genetic variables. A deep and proper assessment of airway samples along with non-invasive biomarkers may have a highly relevant translational significance and enable better knowledge and management of severe asthma.

Risk analysis No major difficulties are expected in view of the study's observational design. No additional costs will be held.