Beyfortus

Pronunciation: BAY-for-TUS
Generic name: nirsevimab-alip
Dosage form: intramuscular injection
Drug class: Other immunostimulants

Medically reviewed by Carmen Pope, BPharm. Last updated on Feb 9, 2024.

What is Beyfortus?

Beyfortus (nirsevimab) is a long-acting monoclonal antibody with activity against the respiratory syncytial virus (RSV) that may be used to protect neonates and infants against lower respiratory tract disease (LRTD) caused by RSV. Beyfortus has been available in the European Union since 31 October 2022. It was FDA-approved in the U.S. on July 17, 2023.

What is Beyfortus used for?

Beyfortus is used to protect against RSV-caused lower respiratory tract infections in neonates and infants born during or entering their first RSV season. A single dose is given.

It may also be used to protect against RSV-caused lower respiratory tract infections in infants who remain vulnerable through their second RSV season such as those with congenital heart disease or chronic lung disease.

How does Beyfortus work?

The active ingredient in Beyfortus is nirsevimab which is a long-acting monoclonal antibody (mAB) that provides passive immunization against RSV to neonates and infants. Passive immunization is when antibodies are given to help prevent or fight certain infectious diseases. Beyfortus helps protect immediately and lasts
for 5 months.

Warnings

Serious hypersensitivity reactions, including anaphylaxis, have been reported with human IgG1 monoclonal antibodies, such as Beyfortus. Beyfortus should not be given to infants and children with a history of serious hypersensitivity reactions, including anaphylaxis, to nirsevimab, or to any of the other ingredients in Beyfortus.
There is a lack of research regarding the coadministration of Beyfortus with other immunoglobulin products, but palivizumab (another monoclonal antibody for RSV) should not be administered to infants who have already received Beyfortus in the same season. However, Beyfortus may be administered in the second season to children who have received palivizumab in their first RSV season but remain vulnerable.

Beyfortus should be used with caution in infants and children with thrombocytopenia, any coagulation disorder, or on anticoagulation therapy.

The safety and effectiveness of Beyfortus have not been established in adults or children older than 24 months of age.

Related/similar drugs

Arexvy, Abrysvo, ribavirin, Synagis, palivizumab, rsv vaccine, pref a-pref b, recombinant, nirsevimab

Before taking

Your child should not receive Beyfortus if they have a history of serious allergic reactions to nirsevimab-alip or any of the ingredients in the injection.

Before your child receives Beyfortus, tell your healthcare provider about all of your child's medical conditions, including if your child:

• has ever reacted Beyfortus or nirsevimab-alip
• has bleeding or bruising problems.

How is Beyfortus administered?

Beyfortus is given by intramuscular injection, preferably into the anterolateral aspect of the thigh, by a healthcare provider. The gluteal muscle is not routinely used as an injection site because of the risk of damage to the sciatic nerve.

The dose is either 0.5mL or 1mL depending on the infant’s body weight.

• Weight < 11lb (<5kg): 50mg given IM using a 0.5mL prefilled syringe.
• Weight ≥ 11lb (≥5kg): 100mg given IM using a 1mL prefilled syringe.

There is limited data available for the use of Beyfortus in extremely preterm infants (gestational age <29 weeks, who are less than 8 weeks of age.

A single dose should be administered before the start of the RSV season, or from birth for infants born during the RSV season.

For infants undergoing cardiac surgery with cardiopulmonary bypass, an additional dose may be administered once the infant is stabilized after surgery, depending on the length of time passed:

First RSV season:

• < 90 days after the first dose, administer 50mg or 100mg depending on body weight
• ≥ 90 days after the first dose, administer a single dose of 50mg regardless of body weight.

Second RSV season:

• < 90 days of the first dose, administer 200mg regardless of body weight
• ≥ 90 days since the first dose, administer 100mg regardless of body weight.

Beyfortus can be administered at the same time as childhood vaccines, at a different injection site. Do not mix Beyfortus with any vaccines or medications in the same syringe or vial.

What are the side effects of Beyfortus?

Get emergency medical help if your child develops signs of an allergic reaction to Beyfortus: symptoms include hives; difficulty breathing; and swelling of the face, lips, tongue, or throat.

The most common side effects of Beyfortus include rash, and pain, swelling, or hardness at the site of your child’s injection.

These are not all of the possible side effects of Beyfortus. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Beyfortus?

Beyfortus does not interfere with reverse transcriptase polymerase chain reaction (RT-PCR) or rapid antigen detection RSV diagnostic assays that employ commercially available antibodies targeting antigenic sites I, II, or IV on the RSV fusion (F) protein.

For immunological assay results that are negative when clinical observations are consistent with RSV infection, it is recommended to confirm using an RT-PCR-based assay.

This list is not complete. Other drugs may interact with Beyfortus, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

What are the ingredients of Beyfortus?

Active ingredients: nirsevimab-alip.
Inactive ingredients: L-histidine, L-histidine hydrochloride, L-arginine hydrochloride, sucrose, polysorbate 80, water for injections.

Available as:

• 50mg in 0.5 mL pre-filled syringe with purple plunger rod
• 100mg in 1 mL pre-filled syringe with light blue plunger rod.

Beyfortus is produced by recombinant DNA technology and is a human immunoglobulin G1 kappa (IgG1κ) monoclonal antibody. Triple amino acid substitution in the Fc region has increased its half-life which increases the length of time it stays effective.

Who makes Beyfortus?

Beyfortus was developed in partnership between Astra Zeneca and Sanofi.

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Further information

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