The Food and Drug Administration (FDA) approved Beyfortus (nirsevimab), a monoclonal antibody developed by Sanofi and AstraZeneca, to protect infants against respiratory syncytial virus (RSV) lower respiratory tract disease (LRTD). This approval is significant as Beyfortus is the first monoclonal antibody to safeguard all infants during their first RSV season.
RSV is a common virus that causes acute respiratory infections across all age groups. However, it is particularly severe in infants, making it the leading cause of hospitalization for children under one in the United States. It surpasses the annual rate of influenza-related hospitalizations by 16 times, with around 590,000 RSV cases in infants requiring medical attention each year.
Beyfortus works as a laboratory-made protein that mimics the immune system's ability to fight viruses like RSV. Administered as a single intramuscular injection before or during the RSV season, one dose of Beyfortus can offer protection.
The approval of Beyfortus was supported by three clinical trials (Trials 03, 04, and 05), where the primary measure of efficacy was the incidence of medically attended RSV lower respiratory tract infection (MA RSV LRTI) within 150 days after Beyfortus administration. Trials 03 and 04, randomized, double-blind, placebo-controlled, multicenter clinical trials, demonstrated that Beyfortus reduced the risk of MA RSV LRTI by approximately 70% and 75%, respectively, compared to the placebo group.
Additionally, Trial 05, which was a randomized, double-blind, active (palivizumab)-controlled, multicenter trial, provided evidence for using Beyfortus in children up to 24 months of age who remain at risk for severe RSV disease during their second RSV season.
Given the seasonal nature of RSV, with transmission primarily occurring in the fall and peaking during the winter, Beyfortus is intended to be available in the U.S. before the 2023-2024 RSV season.
Beyond the U.S., Beyfortus has already obtained approvals in the European Union, Great Britain, and Canada, and its regulatory applications are currently being reviewed in other countries like China, Japan, and several others.
The approval of Beyfortus offers a promising solution to protect infants and young children from the severe consequences of RSV infections.