A Case Report of Refractory Allergic Bronchopulmonary Aspergillosis: The Art of Selection, Discontinuation and Switching Biologics.

BACKGROUND: Biologic therapies have transformed the management of allergic bronchopulmonary aspergillosis (ABPA), improving symptom control and reducing exacerbations. However, a subset of patients exhibits suboptimal or absent response to these therapies. We present a case of refractory ABPA with secondary nonresponse to omalizumab treatment, and subsequently symptom improvement after switching to mepolizumab. CASE REPORT: A 71-year-old male patient was diagnosed with ABPA in August 2020. He was initially managed with inhaled dual therapy, itraconazole, and oral corticosteroids (OCS) for exacerbations. Since 2022, the patient has experienced recurrent acute exacerbations and disease progression, with serum total immunoglobulin E (TIgE) rising to 2150 IU/mL. Subcutaneous omalizumab 600mg every 4 weeks was initiated, which gradually reduced exacerbations and corticosteroids exposure. The biological therapy was then discontinued after 11 months treatment. In 2024, asthma symptoms were uncontrolled despite reinitiation of omalizumab therapy, with 3 exacerbations throughout the year and absolute eosinophils rose to 760 cells/μL. After full evaluation and obtaining informed consent, the patient was switched to mepolizumab in January 2025, which resulted in improved clinical and radiological outcomes. Within 6 months of combination therapy, absolute eosinophils dropped to 30 cells/μL, FEV1 improved from 0.89 to 1.10 L, OCS was gradually tapered and discontinued. The patient continued treatment with mepolizumab, and over a period exceeding 12 months, no recurrence of clinical symptoms or abnormal laboratory findings was observed. CONCLUSION: Mepolizumab was effective in our patient with persistent eosinophilia and secondary nonresponse to omalizumab. Although its long-term efficacy and adverse effects require further follow-up and monitoring, our case adds clinically meaningful evidence and offers valuable insights into personalized biologic decision-making for patients with refractory ABPA.