Asthma loss of control after switch from anti-IL5/5R drugs to dupilumab in severe eosinophilic asthma: a case series.

<bold>Background:</bold> In severe asthma (SA), severe respiratory and systemic complications have been described after switching from an anti-IL5 or IL5R to dupilumab, usually associated with blood hypereosinophilia (HE). Method: French multicenter retrospective study from 2021 to 2023 in patients treated with mepolizumab or benralizumab for severe hypereosinophilic asthma and who presented a worsening of asthma symptoms after switching to dupilumab. <bold>Results:</bold> 20 patients were analysed. The reason for the switch was insufficient control of asthma (A) in 16 or nasal polyposis (NP) in 4 patients. Asthma exacerbations (AE) described in all patients occurred within 6 months after the switch for 85% of the patients and were less severe in the NP group. AEs were always associated with HE, which was greater than 1000/mm3 in 16/20 cases. After the switch, a relapse of eosinophilic granulomatosis with polyangiitis (EGPA) with vasculitis lesions on nasal biopsy and a diagnosis of EGPA were made. In the A group, all patients received repeated or continuous oral corticosteroids (OCS). Dupilumab had to be stopped in 12/16 and continued in 4/16 patients alone or in combination with an anti-IL5/5R. Patients in the NP group did not require continuous OCS and dupilumab could be maintened in 3/4 patients. <bold>Conclusion:</bold> Switching from an anti-IL5/5R to dupilumab may represent a period at risk of severe AE associated with HE. The initiation of dupilumab after failure of an anti-IL5/IL5R must be monitored with particular attention regarding the unmasking/relapse of EGPA. The symptoms seem less severe when the switch is caused by nasal polyposis.