In a letter to the drugmaker, the FDA said the agency approved Beyfortus, an RSV monoclonal antibody, as a defense against RSV lower respiratory tract disease — but that Sanofi has been claiming it protects broadly against RSV disease, which occurs in the lower and upper tracts. Beyfortus has come under scrutiny following reports of at least two infant deaths during clinical trials for the drug.
The U.S. Food and Drug Administration (FDA) is accusing Sanofi of making false or misleading promotional claims about Beyfortus, a preventative treatment for RSV, Fierce Pharma reported.
In a letter to the drugmaker, the FDA said it approved Beyfortus specifically as a defense against respiratory syncytial virus (RSV) lower respiratory tract disease — but that Sanofi has been claiming it protects broadly against RSV disease, which occurs in the lower and upper tracts.
The company has sent providers emails urging them to give the shot to “help prevent RSV disease in infants.”
The promotional materials included other similar statements, including, “Beyfortus is a monoclonal antibody that helps prevent RSV disease starting from Day 1 after injection,” and “Your efforts in immunizing infants against RSV disease can impact the population health burden in your community.”
The FDA said that language creates the “misleading impression” that the drug prevents RSV disease generally.
FDA asks Sanofi to take immediate action to stop misbranding RSV shot
Beyfortus, a monoclonal antibody manufactured by Sanofi and AstraZeneca, was approved by the FDA in 2023. Unlike a vaccine, monoclonal antibodies provide passive immunity by delivering laboratory-produced antibodies designed to protect infants against severe RSV disease.
The FDA emphasized that Beyfortus is specifically approved for the prevention of RSV lower respiratory tract disease — not RSV infection or upper respiratory tract illness generally.
The agency noted that while the promotional emails later referred to protecting infants from “RSV-LRTI,” lower respiratory tract infection, that clarification did not adequately correct the overall impression created by the broader claims appearing earlier in the communications.
“By failing to adequately communicate the indication for Beyfortus, the emails create a misleading impression about the drug’s FDA-approved indication,” the letter states.
The agency concluded that the promotional materials “misbrand Beyfortus” under the Federal Food, Drug, and Cosmetic Act (FD&C Act).
The FDA requested that Sanofi take immediate action to stop disseminating the promotional communications or other materials containing similar representations.
The agency also instructed the company to submit a written response within 15 working days detailing all Beyfortus promotional communications containing comparable claims, along with its plan to discontinue or correct them.
If Sanofi believes its promotional materials do not violate federal law, FDA said the company may provide its reasoning and supporting evidence as part of its response.
Untitled Letter asks for voluntary compliance
The letter was an Untitled Letter issued by the FDA’s Office of Prescription Drug Promotion, which monitors prescription drug advertising and marketing to ensure promotional claims are truthful, balanced, and consistent with approved labeling.
An Untitled Letter is one of the agency’s primary enforcement tools for promotional violations. However, the letter only notifies a company that FDA believes its promotional practices violate the FD&C Act and requests voluntary corrective action.
It does not carry the legal weight of a Warning Letter, which demands corrective action. Failure to adequately respond to a Warning Letter can lead to enforcement actions such as seizures or injunctions.
The agency noted that the concerns described in the letter “do not necessarily constitute an exhaustive list of potential violations,” and reminded Sanofi that it is responsible for ensuring all promotional materials comply with applicable federal law.
Concerns with Sanofi’s products for infants
Last year, the FDA launched a safety review of the RSV shots, including Beyfortus and Merck’s Enflonsia, given to infants to protect against the virus.
Safety questions first surfaced during the summer, when Tracy Beth Høeg, Ph.D., then a senior adviser to the FDA, raised concerns, U.S. Department of Health and Human Services spokesperson Andrew Nixon told Reuters.
Advisers to the Centers for Disease Control and Prevention (CDC) in August 2023 recommended that newborns get the Beyfortus shot. The FDA approved the shots for babies and toddlers in July 2023.
Members of the Advisory Committee on Immunization Practices made the recommendation despite concerns raised by critics at the time that there were several deaths, along with other adverse events, among infants who received the drug during the clinical trials.
In one clinical trial for the drug, there were higher instances of infant deaths among babies who received Beyfortus. In another, immunized babies admitted to the hospital for RSV-related illness stayed longer than non-immunized babies with the same condition, raising concerns that the shot may have worsened their illness.
In October 2024, Sanofi shut down its clinical trial for an RSV vaccine for infants and toddlers, saying that it did not produce the efficacy they were hoping for. A Defender report published last week revealed that, according to documents obtained via a Freedom of Information request, one child died during the trial.
Another Defender report revealed in 2024 that at least two infant deaths reported to the Vaccine Adverse Event Reporting System (VAERS) as occurring after the babies mistakenly received Pfizer’s adult RSV vaccine were likely caused instead by Beyfortus.
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