Pronunciation: EF-gar-TIG-i-mod AL-fa
Generic name: efgartigimod alfa
Brand name: Vyvgart
Dosage form: injection for intravenous infusion
Drug class: Immune globulins

Medically reviewed by Carmen Pope, BPharm. Last updated on Jul 8, 2025.

What is efgartigimod alfa?

Efgartigimod alfa (brand name Vyvgart) is used to treat generalized myasthenia gravis (gMG) in adults who are anti-acetylcholine receptor (AChR) antibody-positive.

• Efgartigimod alfa (Vyvgart) is given as an intravenous infusion (an infusion into the vein) once a week for 4 weeks.
• Efgartigimod alfa + hyaluronidase (Vyvgart Hytrulo) is a formulation of efgartigimod alfa that contains hyaluronidase and is given by subcutaneous injection (under the skin) over 30 to 90 seconds (see Vyvgart Hytrulo or efgartigimod alfa and hyaluronidase for more information).

Efgartigimod alfa's mechanism of action involves attaching to and blocking a protein called neonatal Fc receptor (FcRn) which binds circulating IgG antibodies. When antibodies, including harmful ones, attach to FcRN, their time in the body is extended but those that remain unattached are removed by the body. Harmful IgG antibodies are thought to play a role in conditions such as gMG. Efgartigimod alfa is a fragment of an IgG antibody that keeps some FcRn receptors occupied, so more IgG antibodies, including harmful ones, remain unattached and are removed from the body.

It is a biologic drug made from living cells and belongs to the drug class called neonatal Fc receptor (FcRn) inhibitors. Efgartigimod alfa may also be called an immunomodulator.

Efgartigimod alfa first gained FDA approval on December 17, 2021, for gMG, under the brand name Vyvgart. There is no generic or biosimilar.

Side effects

The most common side effects of efgartigimod alfa are:

• respiratory tract infections
• headache
• urinary tract infections
• injection site reactions.

Serious side effects and warnings

Efgartigimod alfa can cause the following serious side effects.

• An increased risk of infection. Do not administer if you currently have an infection. The most common infections seen in efgartigimod alfa-treated patients are urinary and respiratory tract infections. Call your healthcare provider if you develop signs or symptoms of an infection such as fever, chills, frequent and/or painful urination, cough, pain and blockage of nasal passages/sinus, wheezing, shortness of breath, fatigue, sore throat, excess phlegm, nasal discharge, back pain, or chest pain.
• Allergic reactions (hypersensitivity reactions). These have occurred in some patients treated with efgartigimod alfa. Most were mild or moderate and occurred within one hour to three weeks of medicine administration. Symptoms included rashes, swelling under the skin, and trouble breathing. Hives and serious allergic reactions, such as trouble breathing and a decrease in blood pressure leading to fainting have also been reported in patients treated with efgartigimod alfa. Your doctor will monitor you during your infusion for hypersensitivity reactions. Get emergency medical help if you have signs of an allergic reaction such as hives; difficulty breathing; or swelling of your face, lips, tongue, or throat.
• Infusion-related reactions. Efgartigimod alfa can cause infusion-related reactions. The most frequent
  symptoms and signs reported were high blood pressure, chills, shivering, and chest, abdominal, and back pain.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Related/similar drugs

Before receiving this medicine

Do not receive efgartigimod alfa if you are allergic to efgartigimod alfa, Vyvgart, Vyvgart Hytrulo, or any of the inactive ingredients in the preparation. Efgartigimod alfa can cause serious allergic reactions and a decrease in blood pressure leading to fainting.

To make sure efgartigimod alfa is safe for you, tell your doctor if you:

• have any allergies
• currently have an infection or have had any infections recently
• have received or are scheduled to receive a vaccine (immunization). You should have received all your age-appropriate immunizations before starting efgartigimod alfa
• are pregnant or plan to become pregnant
• are breastfeeding or plan to breastfeed.

Pregnancy

It is not known whether Vyvgart will harm your unborn baby.

Pregnancy Exposure Registry. There is a pregnancy exposure registry for women who use Vyvgart Hytrulo during pregnancy. The purpose of this registry is to collect information about your health and your baby. Your healthcare provider can enroll you in this registry. You may also enroll yourself or get more information about the registry by calling 1-855-272-6524 or going to https://www.Vyvgartpregnancy.com

Breastfeeding

It is not known if Vyvgart passes into your breast milk.  

How is efgartigimod alfa administered?

Efgartigimod alfa is administered intravenously (into a vein) by a healthcare provider in their clinic.

• Efgartigimod alfa takes about an hour to be administered.
• After administration, you will be monitored for hypersensitivity reactions for 30 minutes.

Dosing information

Dose of efgartigimod alfa for gMG (adults)

• 10 mg/kg administered as an IV infusion over 1 hour, 1 time a week for 4 weeks.

Subsequent treatment cycles may be administered based on clinical evaluation.

• It is unknown if it is safe to administer a subsequent treatment cycle within 50 days of the first treatment cycle.

What happens if I miss a dose?

If you miss a dose, ring your healthcare provider to reschedule. The infusion or injection may be administered up to 3 days after the scheduled time. Resume the original dosing schedule until the treatment cycle is completed.

What should I avoid while receiving efgartigimod alfa?

You should avoid receiving live vaccines, such as chickenpox, measles, or mumps vaccines while you are being treated with this medicine.

What other drugs will affect efgartigimod alfa?

Efgartigimod alfa may interact with other prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all other medicines you use, and when you start, stop, or change a dose of any medicine.

Care should be taken when using efgartigimod alfa with other medications that bind to the human neonatal Fc receptor (FcRn) (such as immunoglobulin products, monoclonal antibodies, or antibody derivates containing the human Fc domain of the IgG subclass) because it may reduce the effectiveness of these medications.

Ingredients

Efgartigimod alfa is only available under the brand name Vyvgart. There is no generic.

Active ingredients: efgartigimod alfa 20 mg/mL

Inactive ingredients (Vyvgart): Arginine hydrochloride, polysorbate 80, sodium chloride, sodium phosphate, dibasic, anhydrous, sodium phosphate, monobasic, monohydrate, and water for injection.

Who makes efgartigimod alfa?

Efgartigimod alfa is made by Argenx BV, Industriepark 7, 9052 Zwijnaarde, Belgium, under the brand name Vyvgart and distributed by Argenx US, Inc., 33 Arch Street, Boston, MA 02110.

Efgartigimod alfa Biosimilars

Biosimilar and interchangeable products are biological products that are highly similar to and have no clinically meaningful differences from the reference product.

Reference products

These are biological products that have already been approved by the FDA, against which biosimilar products are compared. There is 1 for efgartigimod alfa.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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