Single-center off-label benralizumab use for refractory hypereosinophilic syndrome demonstrates satisfactory safety and efficacy.

Introduction: Benralizumab is an interleukin 5-receptor-blocking drug registered for the treatment of eosinophilic asthma. It has proven efficient and safe in a small phase-II trial in hypereosinophilic syndrome and is currently being investigated in a larger, randomized phase-III trial. We report on real-world experience with benralizumab in 15 patients with severe Hypereosinophilic syndrome (HES) that were refractory to other treatments or on unacceptable steroid doses. Methods: Fifteen patients with severe HES were treated with compassionate need benralizumab. The measured endpoints were a reduction in peripheral eosinophil count, a reduction of corticosteroid use, adverse events, and clinical response. Results: All subgroups of HES were represented in this cohort and in the case of reactive HES, treatment of the primary cause did not lead to resolution of the eosinophilia. The median time of follow-up was 38 months. Twelve patients reached a normalized peripheral eosinophil count (< 0.05 × 109/L), while the remaining three patients also had a significant reduction from baseline.Of the eight patients initially treated with steroids, five patients were off steroids completely, and three patients had reduced dosages. Eight patients experienced complete symptom resolution, and five partial resolution. No serious adverse events were observed. Conclusion: In conclusion, benralizumab is safe and effective for the treatment of HES.