Merck has received U.S. FDA approval for ENFLONSIA (clesrovimab-cfor), a long-acting monoclonal antibody indicated to prevent respiratory syncytial virus (RSV) lower respiratory tract disease in newborns and infants during or entering their first RSV season. The approval is based on results from the Phase 2b/3 CLEVER trial, which showed that a single 105 mg dose of ENFLONSIA, regardless of weight, reduced the incidence of RSV-associated medically attended lower respiratory infections by 60.5% and hospitalizations by 84.3% over five months. ENFLONSIA offers weight-independent dosing and is designed to provide durable protection across a full RSV season, typically lasting from autumn to spring. “ENFLONSIA combines dosing convenience with strong clinical data showing significant reductions in RSV disease incidence and hospitalizations,” said Dr. Octavio Ramilo, chair of the Department of Infectious Diseases at St. Jude Children’s Research Hospital.
Additional support for the approval comes from the Phase 3 SMART trial, which evaluated ENFLONSIA against palivizumab in high-risk infants. RSV remains a leading cause of infant hospitalization in the U.S., often resulting in serious conditions such as bronchiolitis and pneumonia. ENFLONSIA is contraindicated in infants with a history of severe hypersensitivity to its components. With this approval, Merck advances its efforts to address infectious diseases through targeted, passive immunization solutions for infants during their most vulnerable months.
