FDA advisers recommend approval of monoclonal antibody to protect newborns and young children from RSV

A Food and Drug Administration advisory committee voted overwhelmingly on Thursday to recommend approval of a monoclonal antibody product to protect newborns and young children from RSV.

The Antimicrobial Drugs Advisory Committee voted unanimously to recommend use of nirsevimab — which will be marketed as Beyfortus — in children in the first year of life. In a second vote, the committee voted 19 to 2 to recommend approval of the product for use in high-risk children in the second year of life.

The drug was developed by AstraZeneca. It will be marketed in the United States by Sanofi, which welcomed the committee’s recommendations.

“Most babies hospitalized with RSV are born at term and healthy, which is why interventions specifically designed to protect all infants are likely to result in the greatest impact,” Thomas Triomphe, Sanofi’s executive vice president for vaccines, said after the results of the initial vote were announced.

“We are encouraged by the advisory committee’s positive vote based on the compelling clinical development program supporting nirsevimab and its breakthrough potential to reduce the magnitude of annual RSV burden.”

RSV is a major cause of illness among young children. It is estimated that in any given year, about 400,000 children in this country go to a doctor’s office or a medical clinic for care for lower respiratory tract infections caused by RSV, about 150,000 seek emergency room care, and between 58,000 and 80,000 end up being hospitalized with the illness. It’s estimated that between 100 and 300 children in this country die every year from RSV infection.

The infection is often most severe in very young children, whose lungs are still developing. Designing a vaccine to use in this age group would be challenging as it might take several doses, given over a period of weeks or months, to generate protection — a time during which infants would still be vulnerable to RSV.

Pfizer has come up with a rival approach, developing a vaccine — if approved — that will be given in pregnancy. The antibodies that the pregnant person develops will be shared in utero with the fetus, meaning babies born to vaccinated people will have some protection in the early months of life. That vaccine is also wending its way through the regulatory process.

The AstraZeneca-Sanofi approach would see babies given a single injection of antibodies against RSV either at birth, if they are born during RSV season, or in the autumn, if they are born at a different point in the year. In normal years, RSV season lasts about five months, typically starting around November and peaking in January or February.

Data that AstraZeneca presented to the committee suggested there is a strong protection for at least five months after administration. In a randomized controlled trial, babies who received nirsevimab saw their risk of having RSV infection that required medical care reduced by 70%, and their risk of being hospitalized for RSV infection reduced by 78.4%.

The members of the committee — many of whom are pediatricians — were enthusiastic about the potential of the treatment, noting that the annual crush of RSV cases overwhelms children’s hospitals, compromising the care not just of kids with RSV, but any child needing hospital care.

And they praised AstraZeneca for conducting good, thorough studies in the challenging context of the Covid-19 pandemic.

But they did note that there are questions that remain to be answered, and pressed both the companies and the FDA on the importance of further study.

There are no data, several pointed out, about whether giving nirsevimab to a baby whose mother was vaccinated against RSV during pregnancy would give the infant more protection or would be a waste of the product. And several members of the committee worried that the dose given in the first year of life might be too small to benefit a baby who was 8 months or older when receiving the injection, depending on the size of the baby.

Ighovwerha Ofotokun, an infectious diseases professor at Emory University School of Medicine, raised concerns about how nirsevimab will be used in warmer parts of the country, where RSV is not a winter disease. Tonya Villafana, AstraZeneca’s vice president and global franchise head for vaccines and immune therapies, said the company would work with the FDA and other experts to figure out how to best use nirsevimab in such settings.

Committee chair Lindsey Baden, director of clinical research in the division of infectious diseases at Brigham and Women’s Hospital, also stressed the need for ongoing safety monitoring. Though there were no safety signals in the clinical trials, he said, “safety in 3,000 [children] is not safety in 3 million.”

The FDA is not obligated to follow the advice of the committee, but it would seem unlikely that it would ignore these recommendations, given the high degree of need for tools with which to protect children from respiratory syncytial virus, the No. 1 cause of hospitalizations in infants in this country.

But if the FDA approves Beyfortus, the final word on how it will be used and in whom will rest with the Centers for Disease Control and Prevention, and its expert panel, the Advisory Committee on Immunization Practices. The ACIP can only vote on whether to recommend use of the monoclonal after the FDA approves the product.

Correction: A previous version of this article misspelled Ighovwerha Ofotokun’s first name.