The European Commission (EC) has officially granted marketing authorization for ENFLONSIA™ (clesrovimab), a long-acting monoclonal antibody developed by Merck (MSD) to prevent respiratory syncytial virus (RSV) lower respiratory tract disease in neonates and infants during their first RSV season.
Key Advantages and Mechanism: ENFLONSIA is engineered to deliver rapid and sustained protection for up to five months, covering the typical duration of an RSV season. A significant milestone of this therapy is its simplified, non-weight-based dosing regimen, offering convenience for healthcare providers and families compared to existing options.
Supporting Clinical Data: The approval is backed by evidence from the pivotal Phase 2b/3 CLEVER trial and Phase 3 SMART trial. These studies, published in the New England Journal of Medicine in September 2025, demonstrated:
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Significant reductions in the incidence of RSV-related respiratory disease.
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Substantial decreases in RSV-associated hospitalizations among both healthy and at-risk infants.
Regulatory Reach: The EC’s approval applies to all 27 European Union member states, as well as Iceland, Liechtenstein, and Norway. ENFLONSIA has already secured approvals in major markets including the United States, Canada, and Switzerland. Experts view this approval as a vital public health achievement, with the potential to alleviate the global burden of RSV—a leading cause of infant bronchiolitis, pneumonia, and hospitalization.
Source: https://vohnetwork.com/news/pharma/european-commission-approves-merck-s-enflonsia-clesrovimab-to-prevent-rsv-in-infants-during-first-season