New Drug Approved To Prevent Severe Respiratory Syncytial Virus Infection in Infants

The antibody-based drug Beyfortus (nirsevimab-alip) has been approved by the United States Food and Drug Administration (FDA) to prevent respiratory disease caused by respiratory syncytial virus (RSV) in babies and toddlers.

Reducing the impact of RSV on children

RSV is a contagious virus that infects all age groups but can cause serious illness in infants. Two in three children have an RSV infection within their first year of life, and almost all are infected by the age of two.

Symptoms of RSV infection include runny nose, coughing, fever, low appetite and wheezing. Though most only experience these mild symptoms, it can also cause a severe illness known as lower respiratory tract disease (LRTD), and those experiencing an infection for the first time are particularly susceptible. RSV is the leading cause of hospitalization for infants under one year old, with almost 600,000 cases each year requiring medical treatment.

Beyfortus, developed by Sanofi and AstraZeneca, is a long-acting monoclonal antibody against RSV designed to prevent LRTD throughout an infant’s first year of life with only a single dose. The monoclonal antibody, a lab-made protein, mimics the immune system’s infection-fighting ability and is delivered via an injection into the muscle.

The FDA’s fast-tracked approval comes off the back of three clinical trials in which researchers showed Beyfortus to be highly effective and consistent against RSV LRTD over a 5-month period – the duration of a typical winter RSV season.

“Consistent and sustained efficacy”

The first trial studied 1,453 preterm infants born between 29–34 weeks gestational age and around the time of their first RSV season. Of the 969 infants who received a single dose of Beyfortus, 2.6% experienced RSV LRTD, compared to 9.5% of the 484 infants who received a placebo – a 70% relative reduction in LRTD risk.

A second trial assessed the efficacy of Beyfortus in 1,490 term or late preterm infants. This resulted in a 75% relative reduction in LRTD risk, with 1.2% of 994 treated infants experiencing LRTD compared to 5% of the 296 infants who received a placebo.

Data from a third trial, the results of which are yet to be published, also contributed evidence for the approval of Beyfortus. This trial compared the efficacy of Beyfortus against palivizumab – an existing RSV-targeting monoclonal antibody drug approved in 1998 – in 925 children aged up to 24 months who remain vulnerable to severe illness in their second RSV season due to lung or heart problems.

Trial data also showed the drug was relatively well-tolerated across clinical trials. Common side effects were rashes and reactions at the injection site, while the drug also comes with warnings and precautions for potentially severe allergic reactions and recommends caution for use in some infants with bleeding disorders.

“RSV can cause serious disease in infants and some children and results in a large number of emergency department and physician office visits each year,” said Dr. John Farley, director of the Office of Infectious Diseases in the FDA’s Center for Drug Evaluation and Research. “Today’s approval addresses the great need for products to help reduce the impact of RSV disease on children, families and the health care system.”

This article is a rework of a press release issued by the FDA. Material has been edited for length and content.