What to Know About Fasenra (Benralizumab)

Injectable Drug Used for Severe Eosinophilic Asthma

Fasenra (benralizumab) is an injectable drug used in adults and children 12 years and over who have eosinophilic asthma —a rare form of asthma in which white blood cells called eosinophils are abnormally elevated. Fasenra, a manmade monoclonal antibody, acts on the immune system to help bring eosinophils under control, thus reducing the risk of severe asthma attacks as well as chronic sinusitis and nasal polyps.

Fasenra is used on an ongoing basis as an add-on to standard therapies. Although effective, Fasenra is expensive and may cause side effects. There is no generic available in the United States.

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In November 2017, the U.S. Food and Drug Administration (FDA) approved Fasenra as an add-on treatment for severe eosinophilic asthma.

Eosinophilic asthma is a form of asthma in which the overproduction of eosinophils can amplify inflammation in the airways and cause tissue damage. Compared to non-eosinophilic asthma, in which inflammation is mainly triggered by a type of white blood cell called a neutrophil, eosinophilic asthma is generally more severe and harder to control.

Eosinophils cause inflammation as they degranulate (break apart) and release toxic compounds in the blood. They are influenced by a pre-inflammatory compound known as interleukin-5 (IL-5) that binds to the blood cell and instigates degranulation.

Fasenra works by blocking IL-5 receptors on eosinophils, thereby preventing this process. In addition to being a monoclonal antibody, Fasenra is classified as both an IL-5 antagonist and a biologic drug (i.e., it is made from living cells rather than chemicals).

Fasenra is not used for the treatment of asthma attacks but rather to maintain control of airway inflammation and hyperresponsiveness. Doing so not only decreases the frequency of attacks but also their severity.

A 2017 study published in the New England Journal of Medicine concluded that Fasenra taken every eight weeks reduced the number of asthma attacks by 70% and decreased the need for oral steroid drugs commonly used in people with severe asthma.

There are two other IL-5 antagonists used for the treatment of severe eosinophilic asthma: Cinqair (reslizumab), approved for adults 18 and over, and Nucala (mepolizumab), approved for adults and children 6 years and over.

Off-Label Use

In September 2019, Fasenra was granted orphan drug status by the FDA for the treatment of eosinophilic esophagitis, a chronic inflammatory immune disorder affecting the esophagus (feeding tube). Orphan drug status is a classification in which the FDA recognizes the benefits of a certain drug and provides the manufacturer with tax breaks to encourage clinical research. 

Orphan drug status does not designate the drug as either safe or effective. Still, some doctors have begun exploring the use of Fasenra in treating eosinophilic esophagitis associated with severe gastroesophageal reflux disease (GERD).

Before Taking

Fasenra is only approved for use in treating severe eosinophilic asthma. To confirm whether or not you have this disorder, your doctor will order tests that measure the level of eosinophils in the airways of your lungs.

There are two tests commonly used for this, the first of which is far more accurate:

  • Bronchial biopsy, in which a scope is inserted into your nose or throat to pinch off a tissue sample and/or collect fluids from the airways
  • Sputum induction test, in which you are asked to cough up a sample of mucus for evaluation in the lab

Blood tests may also be ordered, but having a high eosinophil count in the blood doesn't necessarily mean that you will have a high eosinophil count in the airways.

The severity of eosinophilic asthma is determined in part by the number of attacks you have per week, how often you need a rescue inhaler per week, the frequency of nighttime attacks, and the number of times per year you need intravenous steroids to treat an asthma emergency.

In addition to symptoms and medication use, severe asthma may be diagnosed if your forced expiratory volume in one second (FEV1) is less than 60% of the predicted value for your age and sex.

Your doctor will only proceed with prescribing Fasenra if testing confirms that you have eosinophilic asthma.

Precautions and Contraindications

The only absolute contraindication for the use of Fasenra is a known allergy to benralizumab or any other ingredient in the injection.

Because eosinophils are tasked with clearing parasites from the body, people with parasitic worms (helminths) should be treated with broad-spectrum antiparasitic drugs like benzimidazoles before Fasenra treatment is started.

The effect of Fasenra on pregnancy is unknown. Although animal studies have shown no evidence of fetal harm, monoclonal antibodies have the ability to penetrate the placenta during the third trimester of pregnancy (although their effects on an unborn baby remain unknown). It is also unknown if benralizumab can be passed in breast milk.

If you are pregnant, planning to get pregnant, or breastfeeding, speak with your doctor to fully weigh the benefits and risks of Fasenra therapy in your case.


Fasenra is available as a prefilled, single-use syringe. Each injection contains 30 milligrams (mg) of benralizumab per 30-milliliter (mL) dose. There are also Fasenra autoinjector pens containing the same amount of benralizumab per 30-mL dose.

The recommended dose of Fasenra is the same for both adults and children 12 years and over:

  • An induction ("loading") dose of 30 mg/mL every four weeks for the first three doses
  • A maintenance dose of 30 mg/mL every eight weeks thereafter

How to Take and Store

Fasenra is delivered by subcutaneous injection (meaning an injection under the skin). The initial injections may be given at the doctor's office, mainly to teach you how to self-administer the shot. Once you get the hang of it, you can give the shot to yourself or your child at home.

Fasenra is stored in the refrigerator at between 36 degrees F and 46 degrees F. Remove Fasenra from the refrigerator 30 minutes before use to bring it to room temperature. Do not freeze Fasensra.

Though constant refrigeration is ideal, Fasenra can be stored at room temperature (up to 77 degrees F) for no more than 14 days if you are traveling or away from home.

Fasenra solution may either be clear or have a slightly opalescent or yellowish tone. Do not use Fasenra if it is dark or discolored.

Always check the expiration date before using a Fasenra syringe or autoinjector, and discard any product that has expired.

To use the prefilled Fasenra syringe:

  1. Remove the syringe from its packaging by grasping the body of the syringe, not the plunger. You may see tiny bubbles in the solution; this is normal. Do not expel air bubbles before the injection.
  2. Wipe the injection site (upper arm, thigh, or abdomen) with an alcohol swab.
  3. Remove the needle cover immediately before the injection. Do not touch the needle.
  4. Gently pinch the skin at the injection site.
  5. Insert the needle into the skin and depress the plunger completely.
  6. Maintaining pressure on the plunger, remove the needle from the skin.
  7. Once you release the plunger, the needle will retract into the syringe.
  8. Press a cotton ball or swab on the injection site if there is any bleeding. You can place an adhesive bandage on the site if you'd like.

To use the Fasenra autoinjector pen:

  1. Remove the pen from its packaging.
  2. Wipe the injection site (upper arm, thigh, or abdomen) with an alcohol swab.
  3. Remove the green needle cover right before use without touching the needle.
  4. Pinch the skin on the injection site.
  5. Holding the pen at a 90-degree angle, push the needle into the skin.
  6. Hold for 15 seconds. The pen will automatically deliver the dose.
  7. Lift the needle straight out of the skin. The needle guard will automatically slide down and cover the needle.
  8. Use a cotton ball or swab to stop bleeding, if any. Cover with an adhesive bandage if desired.


Discard any expired or used product by placing it in a sharps container, which—when filled—can be properly disposed of a variety of ways, such as at collection sites (e.g., hospitals, pharmacies, health departments), special community pick-ups, and others.

Never place Fasenra, used or not, in your regular trash.

To find out more about some local sharps disposal options in your area, visit SafeNeedleDisposal.org.

Side Effects

As with all drugs, Fasenra may cause side effects. Some are relatively mild and tend to resolve as the body adapts to treatment. Others may be severe and require the termination of treatment.

Taking any drug for a long time can raise concern over side effects related to duration of use. Studies have shown Fasenra to be safe after three years of use, and it is presumed to be safe well beyond this.

Common side effects of Fasenra (affecting 3% or more of users) include:

  • Injection site pain, usually mild
  • Headache
  • Fever, usually mild
  • Sore throat
  • Drug hypersensitivity

In rare instances, a hypersensitive reaction may turn severe and trigger a potentially life-threatening, whole-body allergy known as anaphylaxis. If not treated immediately, anaphylaxis can lead to shock, coma, allergic asphyxiation, heart or respiratory failure, and death.

When to Call 911

Call 911 or seek emergency care if you experience any of the following symptoms after taking a dose of Fasenra:

Warnings and Interactions

Studies have shown that 52% of people on Fasenra will no longer require oral corticosteroid (steroid) drugs after eight weeks of use.

As beneficial as this effect is, you should never stop oral steroids abruptly even if you no longer need them. Doing so can lead to an adrenal crisis in which the level of cortisol (the hormone that corticosteroids mimic) has not yet been restored. This can lead to high fever, nausea, vomiting, rapid heart rate, dehydration, confusion, and coma.

To avoid this, the dose of corticosteroids should be gradually tapered under the supervision of a physician. Depending on the dose and duration of use, the tapering process may last for weeks or months.

Fasenra is a monoclonal antibody generated from living cells, and the body responds to it as it would normal antibodies. Because Fasenra does not alter how the body normally functions, it does not appear to interfere with other drugs or cause drug interactions.

A Word From Verywell

Fasenra is an important drug for people with eosinophilic asthma who are unable to control symptoms with standard drug therapies. Because it works differently than Cinqair and Nucula—which attach to IL-5 rather than to eosinophils—it appears to be more effective.

A notable downside: Fasenra is more expensive than either of the other to IL-5 antagonists (roughly $5,000 versus $3,000 per dose). There is a Fasenra patient assistance program that may reduce your out-of-pocket expenses to $0 if you qualify.

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