Comparison of the General Characteristics of Patients with Severe Asthma Who Switched from Omalizumab to Mepolizumab versus Patients Who Responded to Omalizumab Treatment: A Real-Life Study

<b><i>Introduction:</i></b> Severe asthma is characterized by frequent recurrent airway symptoms and exacerbations, and these affect the quality of life. Biological agents can be used in the treatment of patients with severe asthma if the disease cannot be controlled with standard controller treatment. The aim of this study was to compare the clinical characteristics and laboratory data of patients with severe asthma who were switched from omalizumab to mepolizumab and patients with severe asthma who responded to omalizumab. <b><i>Methods:</i></b> The clinical characteristics and laboratory data of patients with severe asthma who responded to omalizumab and switched from omalizumab to mepolizumab were compared retrospectively. <b><i>Results:</i></b> Evaluation was made of a total of 79 patients, including 64 omalizumab responders and 15 who switched to mepolizumab from omalizumab. After omalizumab and mepolizumab treatment, the annual number of asthma attacks, the use of oral corticosteroid (OCS), the annual number of hospitalizations, and the eosinophil count significantly decreased (omalizumab: <i>p</i> &lt; 0.001, <i>p</i> &lt; 0.001, <i>p</i> &lt; 0.001, <i>p</i> &lt; 0.001, respectively; mepolizumab: <i>p</i> = 0.001, <i>p</i> = 0.001, <i>p</i> = 0.002, <i>p</i> = 0.001, respectively). After omalizumab treatment, the increase in forced expiratory volume in 1 s (FEV1) (%) and asthma control test (ACT) score were determined to be statistically significant (<i>p</i> &lt; 0.001, <i>p</i> &lt; 0.001, respectively). After mepolizumab treatment, the increase in ACT score was significant (<i>p</i> = 0.003). Drug allergy, chronic sinusitis with nasal polyps (CRSwNP), regular use of OCS, and high baseline eosinophil count (cells/µL) were associated with poor response to omalizumab treatment (odds ratio [OR] = 7.86, <i>p</i> = 0.003; OR = 52.92, <i>p</i> &lt; 0.001; OR = 10.16, <i>p</i> = 0.004; OR = 0.99, <i>p</i> = 0.004, respectively). House dust mite sensitivity and high baseline FEV1 (%) were associated with good response to omalizumab treatment (OR = 0.29, <i>p</i> = 0.041; OR = 1.06, <i>p</i> = 0.03, respectively). The blood eosinophil count had diagnostic value in predicting the nonresponsiveness to omalizumab treatment (area under the curve [AUC]: 0.967, <i>p</i> &lt; 0.001, cut-off: 510). <b><i>Conclusion:</i></b> A high pretreatment eosinophil count, concomitant CRSwNP, a history of drug allergy, and regular OCS use may be associated with poor response to omalizumab treatment in patients with severe asthma. Depending on the treatment response, treatment switching can be applied between biological agents. The results of the current study should be supported by multicenter studies.