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What is Fasenra used for and how does it work?

Medically reviewed by Carmen Pope, BPharm. Last updated on March 28, 2023.

What is Fasenra used for? How does Fesenra work?

Official answer

  • Fasenra is used as an add-on, maintenance treatment for people with eosinophilic asthma

  • Fasenra targets and removes cells that play a key role in asthma

  • Fasenra blocks interleukin-5 (IL-5) and enhances the action of natural killer (NK) cells

  • Fasenra depletes the numbers of eosinophils and basophils

Fasenra (benralizumab) is used for the treatment of severe eosinophilic asthma in patients who are 12 years old or older. It is an add-on maintenance treatment, which means it is used on an ongoing basis alongside other treatments to control asthma. It is not a rescue medication.

Fasenra is a monoclonal antibody (IgG1, kappa) that binds to IL-5Rα, the alpha subunit of the human interleukin-5 receptor. It is given via subcutaneous injection, which is an injection given just under the skin. It is injected once every 4 weeks for the first 3 doses, then it’s injected every 8 weeks.

What is eosinophilic asthma?

Eosinophilic asthma is a type of asthma that is often severe. Eosinophils are a type of white blood cell. They are part of the immune system and help fight diseases, including those caused by parasites and bacteria, but they also play a role in regulating inflammation.

Increased numbers of eosinophils are seen in the blood, lung tissue and mucus coughed-up in people with eosinophilic asthma, which is more commonly seen in adults who develop asthma.

How does Fasenra work?

Fasenra works by:

  • Depleting the number of eosinophils
  • Blocking IL-5 from binding to eosinophils, which prevents IL-5 from helping eosinophils to multiply and survive
  • Enhancing the ability of natural killer (NK) cells to kill eosinophils
  • Enhancing the ability of NK cells to kill basophils, which also play a role in the airway-inflammation associated with asthma

Fasenra blocks the action of a cytokine signaling protein called IL-5, which is part of the immune system and plays a key role in airway eosinophilia in people with asthma. Fasenra specifically binds to the IL-5α receptor on eosinophils, preventing IL-5 from binding and its alpha and beta subunits from interacting.

Fasenra also binds to and activates the FcγRIIIa receptor on another type of white blood cell called natural killer (NK) cells. This enhances apoptosis, or programmed cell death, of eosinophils via a process called antibody-dependent cell-mediated cytotoxicity (ADCC). It also enhances the apoptosis of basophils. Basophils are yet another type of white blood cell. They also express IL-5Rα like eosinophils do and play a role in the airway-inflammation associated with asthma.

While Fasenra’s mechanism of action in the body is known, it is not fully understood exactly how its actions help to treat asthma.


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