benralizumab
Benralizumab (Fasenra) is a biologic medicine that targets eosinophils, a type of white blood cell that drives certain kinds of inflammation. It binds to the interleukin-5 receptor on eosinophils and recruits natural killer cells to remove them. It is used as add-on treatment for severe eosinophilic asthma, eosinophilic granulomatosis with polyangiitis, and hypereosinophilic syndrome.
This page is based on EMA and FDA prescribing information for benralizumab, cross-checked with DailyMed labeling and the National Cancer Institute drug dictionary; the mechanism is explained in plain language, and analogies are used only where they stay accurate.
How it works
Explains what the medicine does in the body, not dosing, side effects, or safety.
An analogy
Eosinophils are white blood cells that normally help fight parasites, but in some people they build up in the lungs and blood vessels and cause inflammation. Benralizumab tags each eosinophil with a flag, and the body's own immune sentinels then clear those flagged cells away, so the inflammation calms down.
In simple terms
Benralizumab is an antibody that attaches to a receptor called IL-5Rα found on the surface of eosinophils. Once it binds, it also grabs the attention of natural killer cells, which destroy the tagged eosinophils. This rapidly and nearly completely removes eosinophils from the blood and tissues. With fewer eosinophils driving inflammation, asthma attacks become less frequent, and the blood vessel inflammation seen in eosinophilic granulomatosis with polyangiitis and the tissue damage of hypereosinophilic syndrome can improve.
In depth
Benralizumab is an afucosylated, humanized monoclonal antibody of the IgG1 kappa isotype that binds with high affinity to the alpha chain of the interleukin-5 receptor (IL-5Rα) expressed on eosinophils and basophils. Its afucosylated Fc region enhances binding to FcγRIIIa on natural killer cells, triggering potent antibody-dependent cell-mediated cytotoxicity (ADCC) that rapidly depletes eosinophils through apoptosis. Unlike other anti-IL-5 pathway therapies that neutralize the IL-5 ligand, benralizumab directly targets the receptor-bearing cell, leading to near-complete eosinophil depletion in blood and tissues. By removing the eosinophil-driven inflammatory cascade — including release of major basic protein, eosinophil cationic protein, leukotrienes, and reactive oxygen species — benralizumab reduces airway inflammation in severe eosinophilic asthma, vasculitic inflammation in eosinophilic granulomatosis with polyangiitis, and organ damage in hypereosinophilic syndrome.
See it in motion
A schematic animation of the mechanism — simplified for clarity, not drawn to scale.
Benralizumab tags each eosinophil with a flag
- Eosinophils are white blood cells that normally help fight parasites, but in some people they build up in the lungs and blood vessels and cause inflammation.
- Benralizumab is an antibody that attaches to a receptor called IL-5Rα found on the surface of eosinophils.
- Once it binds, it also grabs the attention of natural killer cells, which destroy the tagged eosinophils.
- With fewer eosinophils driving inflammation, asthma attacks become less frequent, and the blood vessel inflammation seen in eosinophilic granulomatosis with polyangiitis and the tissue damage of hypereosinophilic syndrome can improve.
Target: Interleukin-5 receptor alpha (IL-5Rα)
The alpha subunit of the IL-5 receptor, expressed on eosinophils and basophils; benralizumab binds IL-5Rα and, through its afucosylated Fc region, recruits natural killer cells to induce antibody-dependent cell-mediated cytotoxicity, depleting eosinophils.
Approved uses
Approved uses differ by country and change over time. Always follow your local prescribing information.
Approved uses in European Union
EMA- Add-on maintenance treatment in adult patients with severe eosinophilic asthma inadequately controlled despite high-dose inhaled corticosteroids plus long-acting beta-agonists.
- Add-on treatment for adult patients with relapsing or refractory eosinophilic granulomatosis with polyangiitis.
Approved uses in United States
FDA- Add-on maintenance treatment of adult and pediatric patients aged 6 years and older with severe asthma, and with an eosinophilic phenotype.
- Treatment of adult patients with eosinophilic granulomatosis with polyangiitis.
- Treatment of adult and pediatric patients aged 12 years and older with hypereosinophilic syndrome without an identifiable non-hematologic secondary cause.
Approved uses in United States
DailyMed- Add-on maintenance treatment of adult and pediatric patients aged 6 years and older with severe asthma, and with an eosinophilic phenotype.
- Treatment of adult patients with eosinophilic granulomatosis with polyangiitis.
- Treatment of adult and pediatric patients aged 12 years and older with hypereosinophilic syndrome without an identifiable non-hematologic secondary cause.
Official sources
The statements on this page trace back to these records.
- Fasenra (benralizumab) — Summary of product characteristics and package leaflet, English version
European Medicines Agency
- U.S. Food and Drug Administration: benralizumab prescribing information
U.S. Food and Drug Administration
- DailyMed: FASENRA labeling
DailyMed, U.S. National Library of Medicine
- National Cancer Institute: benralizumab
National Cancer Institute
This page explains how the medicine works — it isn’t the patient leaflet. For anything that applies to you, read the leaflet that came with your medicine or ask your pharmacist.
MedUnfold provides educational content and is not medical advice. Always follow your local prescribing information and healthcare professional.