Mepolizumab: What It Is, Who It Helps, and How It Fits Into Asthma and Eosinophil Treatment

When your asthma won’t respond to inhalers or steroids, mepolizumab, a targeted biologic therapy that blocks interleukin-5 to reduce eosinophil inflammation. Also known as an IL-5 inhibitor, it’s not a quick fix—it’s a long-term tool for people with severe, persistent asthma driven by high levels of eosinophils, a type of white blood cell that causes airway swelling. Unlike broad anti-inflammatories, mepolizumab zeroes in on one specific pathway, making it one of the most precise treatments for a subset of asthma patients who’ve tried everything else.

It’s not just for asthma. Mepolizumab is also approved for eosinophilic granulomatosis with polyangiitis (EGPA), a rare autoimmune disease that attacks blood vessels, and hypereosinophilic syndrome, where too many eosinophils damage organs like the heart or skin. These conditions share a common thread: uncontrolled eosinophil activity. By blocking IL-5, mepolizumab cuts off the signal that tells these cells to multiply and attack. It’s given as a monthly injection, usually in a doctor’s office, and works slowly—most people see fewer flare-ups after three to six months. It doesn’t cure anything, but for many, it means fewer ER visits, less oral steroid use, and a real improvement in daily life.

What makes mepolizumab different from other biologics like benralizumab or reslizumab? It’s the mechanism. While some drugs destroy eosinophils outright, mepolizumab stops them from being made in the first place. That’s why it’s often chosen for patients who still have high eosinophil counts despite other treatments. It’s also one of the few biologics studied in children as young as six. But it’s not for everyone. If your asthma is triggered by allergies or exercise, not eosinophils, this won’t help. Blood tests to check your eosinophil levels are required before starting.

Side effects are usually mild—headache, fatigue, or injection site reactions—but serious reactions like allergic responses or herpes reactivation can happen. People on mepolizumab still need to keep their other asthma meds unless their doctor says otherwise. And while it’s expensive, many insurance plans cover it once you’ve hit the right criteria. It’s not a magic bullet, but for the right person, it’s one of the most effective tools we have.

Below, you’ll find real-world insights on how mepolizumab fits into broader treatment strategies—from how it compares to other biologics, to what happens when patients stop it, and how it interacts with other medications used for chronic inflammation. These aren’t theoretical discussions. They’re based on patient outcomes, clinical data, and the kind of practical questions you’d ask your doctor.