FDA Accepts BLA for Nirsevimab for RSV Prevention for Infants


Developed by Sanofi and AstraZeneca, the single-dose long-acting antibody was designed to help protect all infants from birth through their first respiratory syncytial virus (RSV) season.


The FDA has accepted the biologics license application (BLA) for nirsevimab for the prevention of RSV lower respiratory tract disease in newborns and infants entering or during their first RSV season and for children up to 24 months of age who remain vulnerable to severe RSV disease through their second RSV season.

“RSV can be dangerous for some infants and young children. Each year in the United States, an estimated 58,000-80,000 children younger than 5 years old are hospitalized due to RSV infection,” the Centers for Disease Control and Prevention wrote on its site.

Providers on the frontlines have seen a surge in RSV in the pediatric population in recent months, and the youngest patient population remains the most vulnerable.

"A substantial burden of disease from RSV affects infants, families, and healthcare providers every year," William Muller, MD, PhD, associate professor, Pediatrics, Northwestern University Feinberg School of Medicine and scientific director, Clinical and Community Trials, at the Ann & Robert H. Lurie Children’s Hospital of Chicago, Illinois, said in a statement. "Effective interventions to prevent RSV are a critical need. This year in the US, we’ve seen first-hand how frightening the impact of this respiratory disease is on our patients and how stressful it is on the healthcare system, highlighting the urgency of addressing this problem."

Currently there are no prophylactic therapies or vaccines to protect against RSV. Nirsevimab was developed by Sanofi and AstraZeneca to offer newborns and infants direct RSV protection via an antibody to help prevent lower respiratory tract infection (LRTI) caused by RSV. Monoclonal antibodies do not require the activation of the immune system to help offer timely, rapid and direct protection against disease.

What the Data Shows
The submission is based on results from Sanofi and AstraZeneca’s phase 3 MELODY, phase 2/3 MEDLEY and phase 2b trials. Results across the MELODY and phase 2b trials showed that nirsevimab demonstrated consistent protection of approximately 80%, against medically attended RSV disease with a single dose.

The phase 3 MELODY trial was a randomized, placebo-controlled trial conducted across 21 countries designed to determine efficacy of nirsevimab against medically attended LRTI due to RSV confirmed by reverse transcriptase polymerase chain reaction testing through 150 days after dosing, versus placebo, in healthy late preterm and term infants (35 weeks gestational age or greater) entering their first RSV season. The primary endpoint was met, significantly reducing the incidence of medically attended LRTI, such as bronchiolitis or pneumonia, caused by RSV compared to placebo. Infants were randomized (2:1) to receive a single 50mg (in infants weighing <5kg) or 100mg (in infants weighing ≥5kg) intramuscular injection of nirsevimab or placebo.

Potential Approval Timeline
The Prescription Drug User Fee Act date will be in the third quarter of 2023, and the companies anticipate the potential availability of nirsevimab for next year’s RSV season. “It is our intention to make nirsevimab available, if approved in time, for the 2023/2024 season to help alleviate the burden of RSV on families and the healthcare system,” Thomas Triomphe, executive vice president, Vaccines, Sanofi, said in a statement.

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