Challenges With the Intolerance of Biologics in Severe Eosinophilic Asthma: The Risk of Exacerbations Is Time-Dependent With the Rise of Eosinophils

Patients with severe eosinophilic asthma (SEA) can benefit from biologic therapy but some subjects may present an immune-mediated side effect. These patients will not meet the treatment goals and might have an increased risk of exacerbations. Monitoring these patients by determining blood eosinophil (BE) levels could be one of the tools that may allow a follow-up to prevent a worsening of asthma or exacerbations. The patient was a 50-year-old female with a diagnosis of SEA who had six asthma exacerbations in the last year. Baseline spirometry showed a forced expiratory volume in one second (FEV1) (L) of 0.80 with 34%p (z-score: -4.18) post bronchodilator (BD) and a BE count of 15% (1080 µL cells). After three doses of benralizumab, the spirometry showed an FEV1 (L) of 2.31 with 97%p (z-score: -0.21) post BD and a BE count of 0%. No exacerbations were reported while the patient received biologic medication, but it had to be stopped due to a dermatological allergic reaction. The patient was well-controlled for four months after stopping biologic medication and the BE count also increased, associated with two emergency visits due to exacerbations despite maintenance therapy. Although intolerance or hypersensitivity reactions to the treatment with biologics in asthmatic patients are rare, these patients must discontinue treatment, which increases their risk of exacerbations. In routine medical clinical practice, an easy approach can be made with the follow-up of an accessible and inexpensive test, i.e., the BE count. Its increments should trigger an alert for a closer follow-up and early therapy adjustments.