We treated 10 patients (mean age 58 years, 7 males) with severe eosinophilic asthma with dupilumab for 6 months. Patients at baseline had a mean peripheral blood eosinophil count of 460 103/uL. Total IgE 1154 IU/ml. Baseline FEV1 72% predicted on average, alveolar/capillary diffusion normal as well as 6mWT. Patients showed 5.3 mean exacerbations per year and 5/10 were steroid-dependent. Patients undergoing bronchoscopy with BAL and biopsies of bronchial mucosa. In all patients, we found evidence of moderate eosinophilic infiltrate involving the full-thickness bronchial mucosa. The search for infectious agents as well as auto-antibodies was negative. Baseline BAL: lymphocytes 14%, eos 0-1%. Baseline FENO 63 on average. Baseline ACT 9.7.

After 6 months of therapy, patients improved clinically without presenting complications. ACT 22.6, FENO 23. Peripheral blood eosinophils were increased, mean 1,020 103/uL. Total igE passed to 832 IU/ml. FEV1 slightly increased at 79% predicted. Significant reduction in the number of exacerbations, equal to 1.1 on average. All patients discontinued the systemic steroid therapy. BAL after 6 months shows lymphocytes 12%, eos 0-1%. Bronchial biopsies: persistence of eosinophils in the bronchial mucosa in 7 out of 10 patients. Conclusions: 6-month treatment with dupilumab proved to be safe, effective on exacerbations and on steroid sparing. However, we show the persistence of eosinophils in the bronchial mucosa in patients under dupilumab. More studies are needed to confirm our data.