Machiko Matsumoto-Sasaki,1 Kaoruko Simizu,1 Masanobu Suzuki,2 Masaru Suzuki,1 Hirokazu Kimura,1 Yuji Nakamaru,2 Yoichi M Ito,3 Akihiro Honma,2 Satoshi Konno1 1Department of Respiratory Medicine, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan; 2Department of Otolaryngology-Head and Neck Surgery, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan; 3Data Science Center, Promotion Unit, Institute of Health Science Innovation for Medical Care, Hokkaido University Hospital, Sapporo, JapanCorrespondence: Kaoruko Simizu, Department of Respiratory Medicine, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Kita 15, Nishi 7, Kita-ku, Sapporo, Japan, Tel +81-11-706-5911, Fax +81-11-706-7899, Email okaoru@med.hokudai.ac.jpPurpose: Biologics have been used increasingly for the treatment of severe asthma. However, established guidelines for the selection, switching, or discontinuation of biologics do not exist. We aimed to identify the clinical characteristics of patients with asthma who required switching biologics and the factors associated with switching biologics.Patients and Methods: This was a retrospective study of 42 patients with severe asthma treated with biologics at the Hokkaido University Hospital between 23rd June 2016 and 30th April 2021, when two biologics were available in Japan. We compared the characteristics of subjects who continued and switched biologics. The time to switch the biologics was assessed by type 2 inflammatory biomarkers, pulmonary function indices, and the presence of comorbidities, including the Japanese Epidemiological Survey of Refractory Eosinophilic Chronic Rhinosinusitis (JESREC) score and aspirin exacerbated respiratory diseases (AERD), using the Kaplan–Meier method and a multivariate Cox proportional hazards model.Results: Eight and five patients were treated by mepolizumab and benralizumab at baseline, respectively among the 31% (13/42) who switched the biologics. Subjects who required switching biologics were characterized by high blood eosinophil counts, younger age, JESREC scores of 11 points or higher, and AERD. The time taken to switch biologics was significantly shorter in the subgroups with high JESREC scores (≥ 11) or AERD, compared with their counterparts with low JESREC scores or without AERD (both, P < 0.05). JESREC scores of ≥ 11, but not the presence of AERD, were associated with time to switch biologics.Conclusion: The presence of eosinophilic chronic rhinosinusitis based on JESREC scores of ≥ 11 and younger age were factors associated with switching biologics in asthma.Keywords: aspirin-exacerbated respiratory disease, asthma, biologics, comorbidities, eosinophilic chronic rhinosinusitis