[Adverse reactions to biotechnological agents targeting IL-5].

Case report: A 24-year-old woman with asthma (2013) and allergic rhinitis (2014) was treated for 3 years with subcutaneous immunotherapy, inhaled salmeterol/fluticasone, and external antihistamines. She presented to our department (2019). Upon admission, her asthma persisted with uncontrolled asthma, daily use of a rescue inhaler, and persistent moderate-severe rhinitis. Asthma treatment was adjusted according to guidelines, reaching step 4 of treatment, with persistent lack of control (ACT 16 points), meeting criteria for starting Benralizumab 30 mg (July 26, 2024). Two doses were completed with clinical improvement (ACT). However, during two doses, the patient presented with fever, headache, myalgia, and arthralgia, so treatment was discontinued. Symptoms worsened. A decision was made to switch from the biotechnological agent to mepolizumab (February 4, 2025), with adverse effects after the third dose.

Conclusion: A percentage of patients with asthma presented with severe symptoms, 80% with an eosinophilic phenotype, associated with difficult control and increased exacerbations. Monoclonal antibodies are indicated in these patients. Benralizumab, which targets IL-5Rα, induces eosinophil depletion through antibody-mediated cytotoxicity. Several studies (MELTEMI) have been conducted to evaluate the safety of long-term use. The most common non-serious adverse effects include upper respiratory tract viral infections (47.3%), while less common adverse effects are headache and arthralgia, which account for 20.9% and 6.4%. Biotechnological agents reduce exacerbations, reduce corticosteroid use, and improve control and quality of life. However, they are not exempt from adverse effects, and even the less common ones should be identified to assess continued treatment.