Beyond the Eosinophil: Understanding the Impact of Eosinophil Depletion on T2 Inflammation. (BEUTI)

Benralizumab is a relatively new treatment that is approved by NICE for patients with severe asthma and ongoing eosinophilic inflammation that remains poorly controlled despite high dose inhaled corticosteroid medication. Benralizumab targets a receptor on the surface of eosinophils called IL-5R leading to the rapid death of these cells and consequently a reduction in airways inflammation. In clinical trials, benralizumab has been shown to reduce both symptoms and the number of asthma attacks suffered by those with severe eosinophilic asthma. However, it remains unclear whether this clinical efficacy relates purely to the removal of the eosinophil, or additionally to the impact of this on other parts of the immune system including activation of type-2 (T2) inflammation pathways.

The clinical effectiveness of benralizumab is evident across phase 3 and real world studies which has reaffirmed the central role that the eosinophil plays in disease and exacerbation pathogenesis in patients with severe asthma. However, whilst it is generally believed that this fundamentally reflects the removal of eosinophils and their toxic granules and mediators from the airway, the full impact of benralizumab on T2 immunity may be much broader.

Firstly, benralizumab-treated patients stop exacerbating when they encounter respiratory viruses such as rhinovirus, suggesting that the deficient anti-viral immune responses present in many uncontrolled T2-high asthmatics are restored upon benralizumab. Secondly, our centres' finding that patients continue to remain well-controlled despite significantly reducing their inhaled corticosteroid (ICS) use following initiation of benralizumab suggests that the other elements of T2 inflammation (including IL-13 driven pathways) are either unimportant or suppressed (d'Ancona et al., Allergy 2021, vol; 76(7):2238-2241). Thirdly our observation that benralizumab is very effective in patients with high fractional exhaled nitric oxide (FeNO) levels (indicating increased IL-13-driven activation) and that treatment significantly reduces FeNO levels suggests that benralizumab directly or indirectly suppresses IL-13 pathways (Hearn et al., J Allergy Clin Immunol Pract, 2021, Vol;9(5):2093-2096). Taken together, there is an increasing body of data supporting the notion that benralizumab has far-reaching anti-T2 effects that underpin its excellent efficacy in clinical practice. Through the use of novel techniques including spatial transcriptomics of bronchial biopsies this proposal aims to define and describe these effects.

Study Hypothesis:

The depletion of eosinophils by benralizumab leads to additional inhibitory effects on T2 inflammation which collectively underpins the improvements in multiple clinical domains and reduction in T2 biomarkers observed in real world cohort studies.

The important research questions we will aim to answer:

1. What is the effect of benralizumab on T2 signalling. Can benralizumab modulate T2-signalling and/or gene expression in addition to triggering eosinophil and basophil depletion? ii) What additional cell types (e.g. ILC2, alveolar macrophages, mast cells, bronchial epithelial cells, airway smooth muscle) are regulated by benralizumab? iii) Does the marked reduction in exacerbations observed with benralizumab partly reflect restoration of the deficient anti-viral immune responses seen in patients with severe asthma?

The investigators plan to take samples of cells from the airways during a bronchoscopy (a camera test looking into the lungs) before starting benralizumab and after 12 weeks of treatment. These investigations will allow us to better understand how benralizumab affects the cells within the airways.

BEUTI study primary objective is to investigate the impact of benralizumab treatment on lung inflammation and airway structure in patients with severe eosinophilic asthma. Its secondary objective is to understand if benralizumab treatment affects response to infection with respiratory viruses such as the common cold virus (rhinovirus) and SARS CoV2.

Benralizumab will be commenced according to UK NICE severe asthma guidance with 30mg sub cutaneous dosing every 4 weeks for first 3 doses, followed by every 8 weeks.

The BEUTI study will have a total of 8 visits with 2 bronchoscopies (to collect airway cells and blood cells) at visit 2 and visit 8.

Throughout the study, information regarding their asthma symptoms, adverse events and lung function will be collected.

Asthma control score and quality of life questionaire (ACQ-6/mAQLQ). Breathing tests will be performed (spirometry, fractional exhaled nitric oxide (FeNO)).