CLINICAL CHARACTERISTICS ASSOCIATED WITH MUCUS PLUGGING IN SEVERE EOSINOPHILIC ASTHMA AND THE EFFECTIVENESS OF BENRALIZUMAB TREATMENT

Background Eosinophil-rich mucus plugs are a recognised feature of asthma and are believed to contribute to airflow obstruction. However, little is known about the incidence of plugging in severe eosinophilic asthma (SEA) and the relationship of plugging to other characteristics of this phenotype. In addition, it is unknown whether patients with evidence of plugging have a differential response to the eosinophil depleting anti-IL-5R therapy benralizumab. Methods Pre-biologic CT scans of patients with SEA treated with benralizumab were assessed by two radiologists independently. Patients were given a mucus score out of 20 (per segment plugged; score of 1–3 classed as plugging-low, score 34 as plugging-high). Baseline characteristics and clinical outcome following 1 year of treatment was compared between patients with and without evidence of plugging. Results CT scans of 116 patients with SEA were reviewed. 69/116 (59.5%) exhibited mucus plugging of which 40/116 (34.5%) were classed as plugging-high. Median (IQR) number of segments plugged was 4 (2–10.5). Baseline characteristics were similar between the plugging and no-plugging groups, with a trend towards lower baseline FEV1 in the plugging group (p=0.06). Nasal polyposis was more frequent in the plugging-high group (45%) compared to plugging low (24%) and unplugged (21%) groups (ANOVA p=0.04). Response to benralizumab at 1 year was comparable between those with and without plugging: AER reduction 3.67+/- 4.1 vs 3.17+/-3.47; change in ACQ6 0.73+/-1.1 vs 0.77+/-1.38; change in FEV1% 6.72+/-17.35 vs 6.50+/-18.3 (all p=NS). The number of plugged segments at baseline did not correlate with improvement in FEV1. Discussion Mucus plugging is identified in 60% of patients with SEA and is more commonly seen at high levels in patients with co-morbid nasal polyposis. Individuals with SEA and mucus plugging have a similar clinical response to eosinophil targeted therapy with benralizumab compared to patients with SEA but absent plugging on CT imaging.