New Drug Approved for Preventing RSV in Newborns, Tots

The FDA approved nirsevimab (Beyfortus) on Monday for preventing respiratory syncytial virus (RSV)-related lower respiratory tract infections in infants and very young children.

Delivered as a single intramuscular injection, the monoclonal antibody is indicated for babies born during or entering their first RSV season, as well as for high-risk children up to 2 years of age during their second season. In the U.S., RSV typically starts circulating in the fall and peaks by winter.

“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,” John Farley, MD, MPH, director of the Office of Infectious Diseases at FDA’s Center for Drug Evaluation and Research, said in a statement. “Today’s approval addresses the great need for products to help reduce the impact of RSV disease on children, families, and the healthcare system.”

Until Monday, no drug had been approved for such a broad indication, with palivizumab (Synagis) limited to RSV prevention for high-risk kids.

Nirsevimab’s approval follows a resounding endorsement from the agency’s Antimicrobial Drugs Advisory Committee, which last month voted unanimously in favor of the monoclonal antibody’s risk-benefit profile.

RSV can affect people of any age, typically manifesting as cold-like symptoms, but infants and older adults are most at risk for severe outcomes.

RSV is the leading cause of hospitalization in U.S. infants, with roughly 1% to 3% winding up in the hospital each year for these infections. During an initial infection, some infants develop pneumonia, bronchiolitis, or other lower respiratory tract disease requiring medical care. According to the FDA, infants most at risk of severe RSV include those born premature, babies with chronic lung disease of prematurity, and those with significant congenital heart disease.

Support for nirsevimab’s approval in neonates and infants came from a randomized phase IIb trial and the phase III MELODY trial involving 1,490 healthy late-preterm and term infants. In the placebo-controlled MELODY trial, a single dose of nirsevimab reduced the risk of a medically attended lower respiratory tract RSV infection by 74.5% (95% CI 49.6-87.1) during the 150 days after administration compared with placebo, with absolute rates of 1.2% versus 5%, respectively (P<0.001).

Safety and pharmacokinetic data from a randomized phase II/III multicenter study (MEDLEY) supported the indication for use of nirsevimab during a second RSV season in vulnerable children up to 2 years. The double-blind trial compared nirsevimab with palivizumab in 925 preterm infants and infants with chronic lung disease of prematurity or congenital heart disease.

In the trials, the most common adverse events associated with nirsevimab included rash and injection site reactions. The FDA warned about the potential for serious hypersensitivity reactions, including anaphylaxis (noting that these have been seen with other IgG1 monoclonal antibodies), and said the drug should be given “with caution” to those with clinically significant bleeding disorders.

Drugmaker AstraZeneca said nirsevimab will be available in the U.S. ahead of the upcoming RSV season.