Merck is aiming to expand the use of its RSV preventive treatment Enflonsia to cover children under two at increased risk during their second RSV season, with an FDA decision expected in March 2027, based on promising Phase 3 trial data.
Merck is seeking to widen the use of its respiratory syncytial virus preventive treatment Enflonsia to cover children under 2 who remain at increased risk in their second RSV season, as the US Food and Drug Administration begins reviewing the application. The company said the filing was accepted as a supplemental biologics licence application and that the regulator has set a target decision date of March 22, 2027.
The proposed extension would allow use in children vulnerable to severe RSV disease because of conditions such as chronic lung disease or congenital heart disease, including some born very preterm. According to Merck, the request is backed by data from the Phase 3 SMART trial, which studied the drug in infants and children at elevated risk over two RSV seasons and compared it with palivizumab in certain patients.
Enflonsia, known scientifically as clesrovimab-cfor, was first approved by the FDA in 2025 for infants entering their first RSV season. Merck says it is the only preventive option for RSV lower respiratory tract disease in infants that is given without weight-based dosing, using a single 105 mg intramuscular injection designed to protect for about five months.
RSV remains a major cause of hospitalisation in infants and can lead to bronchiolitis and pneumonia. Merck said the second-season filing reflects an unmet need for children whose risk does not end after their first winter of exposure. The company also said European regulators accepted a similar application in July 2026, signalling a broader push to expand the drug’s reach beyond newborns and young infants.
Disclaimer: This content is for informational purposes only and is not intended to be a substitute for professional medical judgment, advice, diagnosis, or treatment.
