Merck , known as MSD outside the United States and Canada, announced that the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) has recommended the approval of its investigational monoclonal antibody, ENFLONSIA™ (clesrovimab). The therapy is intended for the prevention of Respiratory syncytial virus (RSV) lower respiratory tract disease in newborns and infants during their first RSV season.
The CHMP’s positive opinion will now be reviewed by the European Commission (EC) for marketing authorization across the European Union (EU), Iceland, Liechtenstein, and Norway, with a final decision expected before the end of the year.
“As one of the most pervasive seasonal respiratory infections and a leading cause of infant hospitalization globally, RSV continues to place a significant burden on families and health care systems,” said Dr. Macaya Douoguih, vice president, Therapeutic Area Head, Global Clinical Development, Merck Research Laboratories. “With strong clinical data paired with convenient dosing, this positive opinion recognizes ENFLONSIA as an important new potential option to help protect infants in Europe.”
ENFLONSIA is a long-acting preventive monoclonal antibody designed to provide immediate and durable protection for up to five months—the duration of a typical RSV season—using a single fixed dose, regardless of infant weight.
It is not recommended for infants with known serious hypersensitivity reactions, including anaphylaxis, to any of its components.
The CHMP’s recommendation is supported by results from the pivotal Phase 2b/3 CLEVER (MK-1654-004, NCT04767373) trial, which evaluated ENFLONSIA’s safety and efficacy in preterm and full-term infants up to one year of age, and the Phase 3 SMART (MK-1654-007, NCT04938830) trial, which compared ENFLONSIA to palivizumab in infants at increased risk for severe RSV. Findings from both trials were recently published in the New England Journal of Medicine.
ENFLONSIA received approvals in the United States and United Arab Emirates in June 2025 and is currently under review in several other markets worldwide.