FDA Approves Merck’s RSV Drug for Babies
- The Food and Drug Administration (FDA) has approved Enflonsia (clesrovimab), a monoclonal antibody developed by Merck, for protecting infants younger than 12 months against respiratory syncytial virus (RSV).
- Merck has set the wholesale price of Enflonsia at $556 per dose, the same as Sanofi and AstraZeneca’s Beyfortus (nirsevimab).While the price is the same, Enflonsia features a...
- Currently, Enflonsia is approved only for infants in their first RSV season.
The FDA has greenlit merck’s Enflonsia (clesrovimab) for RSV prevention in babies under 12 months, offering a new shield against this common respiratory virus.This approval provides another potent option, priced similarly to competitor Beyfortus at $556 per dose, but with a simplified single-dose injection. Merck‘s Enflonsia could streamline administration, as highlighted by the company.The recent news also raises questions about the upcoming Advisory Committee on Immunization Practices (ACIP) meeting, though Health and Human Services has confirmed it will proceed. Read further for details from news Directory 3, including how this new treatment compares in terms of efficacy and availability, and what that means for healthcare providers and families. Discover what’s next as the medical community assesses Enflonsia’s impact.
FDA Approves Merck’s Enflonsia for RSV Prevention in Infants
Updated June 09, 2025
The Food and Drug Administration (FDA) has approved Enflonsia (clesrovimab), a monoclonal antibody developed by Merck, for protecting infants younger than 12 months against respiratory syncytial virus (RSV). This approval introduces a third option for RSV prevention,potentially impacting the cost and accessibility of these treatments.
Merck has set the wholesale price of Enflonsia at $556 per dose, the same as Sanofi and AstraZeneca’s Beyfortus (nirsevimab).While the price is the same, Enflonsia features a single-dose regimen for all babies, which may simplify administration compared to Beyfortus, which has two weight-based dosages. Paula Annunziato, Merck’s senior vice president for clinical research, noted this simpler approach could ease logistical challenges for health care providers.
Currently, Enflonsia is approved only for infants in their first RSV season. Beyfortus, in contrast, is approved for all babies in their first RSV season and for high-risk infants in their second. Merck is studying Enflonsia against Synagis, an existing RSV monoclonal antibody for high-risk infants. Positive results could lead to Merck seeking approval for Enflonsia’s use in high-risk children during their second RSV season.
The Advisory Committee on Immunization Practices (ACIP) was expected to vote on recommending Enflonsia at its late June meeting. However, the recent dismissal of the entire committee raises questions about the meeting’s functionality.Health and Human services maintains the meeting will proceed as scheduled.
Merck anticipates taking orders for Enflonsia in July,with shipments expected in time for the 2025 RSV season. Annunziato emphasized the importance of enflonsia as a prevention tool for families, infants, and the health care system.
Clinical trials demonstrated that the monoclonal antibody injection reduced medically attended lower respiratory infection caused by RSV by over 60% and RSV-related hospitalizations by over 84%.
The introduction of Enflonsia marks further progress in RSV prevention. Pfizer’s Abrysvo vaccine, designed for pregnant individuals, transfers protective antibodies to the fetus. Monoclonal antibodies like Enflonsia and Beyfortus can be administered to infants born outside the vaccination window to provide immediate protection against RSV.
what’s next
With the FDA approval secured, Merck will focus on manufacturing and distributing Enflonsia in time for the upcoming RSV season. The medical community will be watching to see how the single-dose regimen impacts adoption and how the product performs against its competitors in real-world settings.