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Mepolizumab Mechanism — RACP Adult Medicine MCQ

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EasyRespiratoryMepolizumab MechanismRACP Adult Medicine

A 50-year-old woman with severe eosinophilic asthma (blood eosinophils 800 cells/μL) has failed high-dose ICS/LABA/LAMA and is on frequent oral prednisolone courses (6 courses/year). She has steroid-related side effects (osteoporosis, diabetes, weight gain). She is commenced on mepolizumab (anti-IL5). After 4 months, her exacerbation frequency has decreased by 50% and she has been able to reduce prednisolone. What is the primary mechanism of mepolizumab?

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Correct answer: B — Anti-IL5 (depletes eosinophils)

Mepolizumab (and reslizumab) are anti-IL5 monoclonal antibodies that deplete circulating and tissue eosinophils. Benralizumab targets the IL-5 receptor alpha (anti-IL5Rα) and causes direct eosinophil apoptosis via ADCC. These are indicated for severe eosinophilic asthma (≥300 cells/μL). They significantly reduce exacerbation rates (~50%), oral steroid use, and improve quality of life. Not effective for non-eosinophilic asthma.

Reference: Australian Asthma Handbook – 2024; GINA 2024; DREAM/MENSA Trials