What class of drug is benralizumab? A Targeted Approach to Asthma

October 8, 2025 •

3 min read

Approved by the FDA in 2017, benralizumab is a biologic medication designed for the add-on maintenance treatment of severe eosinophilic asthma. This article explains what class of drug is benralizumab and its unique mechanism of targeting the interleukin-5 (IL-5) receptor to reduce eosinophil-driven inflammation.

Quick Summary

Benralizumab is a biologic drug classified as a monoclonal antibody and an interleukin-5 receptor inhibitor. It specifically targets and depletes eosinophils, which are a major driver of inflammation in severe asthma.

Key Points

Drug Class: Benralizumab is a biologic medication, a monoclonal antibody, and an interleukin-5 receptor inhibitor.
Mechanism of Action: It uniquely causes programmed cell death (apoptosis) of eosinophils and basophils via antibody-dependent cell-mediated cytotoxicity (ADCC).
Target: Its target is the interleukin-5 receptor alpha (IL-5Rα) subunit on the surface of eosinophils, not the IL-5 cytokine itself.
Targeted Therapy: Benralizumab is indicated for severe eosinophilic asthma and eosinophilic granulomatosis with polyangiitis (EGPA).
Result: It leads to rapid and nearly complete depletion of eosinophils, which helps reduce inflammation and asthma attacks.
Formulation: The medication is administered as a subcutaneous injection.

Understanding benralizumab's primary drug classes

Benralizumab (brand name Fasenra) is classified as both a biologic medication and a monoclonal antibody. As a biologic, it's derived from living organisms, offering a targeted approach to immune system pathways. Monoclonal antibodies are lab-made antibodies designed to bind to specific targets. Benralizumab's structure allows it to bind to a particular protein on certain immune cells.

A more specific classification: Interleukin-5 Receptor Inhibitor

Benralizumab is more specifically classified as an interleukin-5 receptor alpha (IL-5Rα) inhibitor. It targets the IL-5Rα subunit found on eosinophils and basophils, which are immune cells involved in asthma inflammation. By binding to this receptor, benralizumab blocks signals that promote eosinophil survival.

The unique mechanism of action

Benralizumab stands out among IL-5 pathway inhibitors because it directly targets the receptor and rapidly depletes eosinophils. This mechanism is known as antibody-dependent cell-mediated cytotoxicity (ADCC). The process involves benralizumab binding to IL-5Rα on eosinophils and basophils, its afucosylated structure attracting natural killer (NK) cells, and these NK cells inducing programmed cell death (apoptosis) in the targeted eosinophils. This results in a significant reduction of eosinophils in the blood and bone marrow.

Benralizumab's mechanism vs. other IL-5 pathway drugs

Here's how benralizumab compares to other biologics that target the IL-5 cytokine itself:


Feature	Benralizumab (Fasenra)	Mepolizumab (Nucala) & Reslizumab (Cinqair)
Target	Interleukin-5 receptor alpha (IL-5Rα) on the surface of eosinophils and basophils.	The interleukin-5 (IL-5) cytokine in the bloodstream.
Mechanism of Depletion	Induces apoptosis (programmed cell death) in eosinophils and basophils via Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC).	Blocks the IL-5 cytokine, which inhibits eosinophil maturation and survival.
Depletion Profile	Rapid and near-complete depletion of eosinophils in blood and tissues.	Reduces circulating eosinophil levels but is less effective at depleting tissue-resident eosinophils compared to benralizumab.
Action on Cytokine	Blocks the receptor, independent of IL-5 ligand levels.	Neutralizes the IL-5 cytokine, but other cytokines may still signal via the receptor.

Who is benralizumab for?

Benralizumab is an add-on maintenance treatment for specific conditions driven by high eosinophil levels, not for acute asthma attacks. It is used for:

Severe Eosinophilic Asthma: For individuals aged 6 and older with severe asthma uncontrolled by high-dose standard treatments. This type of asthma is marked by elevated eosinophil levels.
Eosinophilic Granulomatosis with Polyangiitis (EGPA): An adult condition involving blood vessel inflammation and high eosinophils.

List of key features

Targeted Therapy: Specifically targets the IL-5Rα.
Biologic Origin: A monoclonal antibody.
ADCC Mechanism: Utilizes natural killer cells for targeted cell death.
Effective for Severe Asthma: Reduces asthma attacks and can improve lung function.
Subcutaneous Administration: Given as an injection under the skin.
Steroid-Sparing: May reduce or eliminate the need for oral corticosteroids.
Not a Rescue Inhaler: For long-term control, not immediate relief.

Conclusion

Benralizumab is a biologic medication, classified as a monoclonal antibody and an interleukin-5 receptor inhibitor. Its unique mechanism involving ADCC and targeting the IL-5Rα leads to the depletion of eosinophils. This makes it an effective add-on treatment for severe eosinophilic asthma and EGPA by addressing the root cause of inflammation. You can find more information in the MedlinePlus entry for Benralizumab Injection.

Frequently Asked Questions

No, benralizumab is not a steroid. It is a biologic medication that works on a specific part of the immune system to reduce inflammation in severe eosinophilic asthma. It can help reduce or eliminate the need for oral steroids in some patients.

Benralizumab binds directly to the IL-5 receptor on eosinophils, triggering their destruction. Other inhibitors, like mepolizumab, block the IL-5 cytokine, which prevents it from activating eosinophils.

Benralizumab should not be used to treat a sudden asthma attack. It is not a rescue medication. It is a long-term maintenance treatment for severe asthma caused by eosinophils.

Benralizumab is given as a subcutaneous injection, which can be done by a healthcare professional or, for adults and some children, self-administered at home using a prefilled autoinjector pen.

Common side effects include headache and a sore throat. Some individuals may also experience reactions at the injection site.

No, benralizumab is specifically indicated for severe eosinophilic asthma, which is a subtype driven by high levels of eosinophils. A doctor will perform tests to confirm a high eosinophil count before prescribing this medication.

For asthma, benralizumab is typically administered once every four weeks for the first three doses, and then once every eight weeks thereafter. For EGPA, the dosing is usually once every four weeks.