Hypereosinophilia during dupilumab treatment in patients with chronic rhinosinusitis with nasal polyps

Background: Increased blood eosinophil count (BEC) is common in patients under dupilumab treatment for chronic rhinosinusitis with nasal polyps (CRSwNP). This study investigated the prevalence and consequences of hypereosinophilia and to help define patients at risk. Methods: Real-life, prospective observational cohort study of patients treated with dupilumab for severe CRSwNP. Eligible patients were adult and biological-naïve (N=334). All BEC values at baseline and during treatment were reported. Patients with a follow-up of ≥ 1 year were included to define patients at risk for hypereosinophilia by comparing baseline BEC values (N=218). Furthermore, clinical characteristics and therapeutic consequences for patients with BEC ≥ 3.0 were noted. Results: Hypereosinophilia developed in a minority of patients, with a peak at week 12 (16.2% with BEC ≥ 1.5, and 1.7% ≥ 3.0) in cross-sectional analysis. BEC ≥ 1.5 developed in 28.9% and BEC ≥ 3.0 in 4.6% of cases with a minimal 1-year follow-up. Baseline BEC was significantly higher for patients developing BEC ≥ 1.5 and BEC ≥3.0, with an optimal cut-off point of 0.96 to predict developing BEC ≥ 3.0. Conclusions: Blood eosinophil count (BEC) ≥ 1.5 is transient and usually abates with no therapeutic interventions and BEC ≥ 3.0 is rare. Hypereosinophilic syndrome did not occur and switching to a different biological was rarely employed. A baseline BEC of ≥1.0 can be a reason for extra caution.