The FDA has approved clesrovimab-cfor (Enflonsia; Merck) for the prevention of respiratory syncytial virus (RSV)-associated lower respiratory tract infection.1
The approval was based in part on data captured in phase 2b/3 (NCT04767373) and phase 3 (NCT04938830) trials, both of which were conducted among infants. This long-acting monoclonal antibody is designed to provide protection against RSV for up to 5 months following administration.
“RSV disease is the leading cause of infant hospitalization in the U.S. and can lead to serious respiratory conditions like bronchiolitis and pneumonia,” Octavio Ramilo, MD, chair of the Department of Infectious Diseases at St. Jude Children’s Research Hospital and investigator for the CLEVER (MK-1654-004) and SMART (MK-1654-007) trials, said in a prepared statement about the approval. “Enflonsia combines dosing convenience with strong clinical data showing significant reductions in RSV disease incidence and hospitalizations, making it a promising new intervention to help protect infants from RSV.”
Enflonsia is indicated for newborns and infants born during or entering their first RSV season. It is contraindicated for infants with a history of anaphylaxis to any of its components.
Reference
- US FDA approves Merck’s Enflonsia (clesrovimab-cfor) for prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in infants born during or entering their first RSV season [press release]. Merck. June 9, 2025. Accessed July 8, 2025. www.merck.com/news/u-s-fda-approves-mercks-enflonsia-clesrovimab-cfor-for-prevention-of-respiratory-syncytial-virus-rsv-lower-respiratory-tract-disease-in-infants-born-during-or-entering-their-fir/