Events Details
European Commission Approves Merck’s ENFLONSIA™ (clesrovimab) for the Prevention of Respiratory Syncytial Virus (RSV) Lower Respiratory Tract Disease in Infants During Their First RSV Season
Monday, April 20, 2026
Merck, known as MSD outside the United States and Canada, has announced that the European Commission (EC) has approved ENFLONSIA™ (clesrovimab). It is used to prevent respiratory syncytial virus (RSV) lower respiratory tract disease in newborns and infants during their first RSV season. ENFLONSIA should not be used in infants who are allergic to the drug or any of its ingredients.
ENFLONSIA is a long-acting monoclonal antibody designed to give quick and lasting protection for about five months (a typical RSV season) with a fixed dose. The EC approval allows it to be marketed in all 27 European Union countries, as well as Iceland, Liechtenstein, and Norway. However, availability will differ by country depending on reimbursement approvals and other factors.
According to Paolo Manzoni, RSV can lead to serious illnesses like bronchiolitis and pneumonia and is a major cause of infant hospitalizations worldwide. He noted that ENFLONSIA, supported by strong clinical data from the CLEVER and SMART trials, offers a new option to reduce RSV cases and related hospitalizations, while also being convenient to use.
Macaya Douoguih from Merck stated that this approval is an important step in expanding access and reducing the global burden of RSV. He added that the company is committed to providing this new preventive option to families and healthcare providers.
The approval is based on results from the Phase 2b/3 CLEVER trial and early data from the Phase 3 SMART trial, which evaluated the safety and effectiveness of ENFLONSIA in infants, including those at higher risk. These results were published in the New England Journal of Medicine in September 2025.
ENFLONSIA is already approved in the United States, Canada, Switzerland, and several other countries for use in infants during their first RSV season. Regulatory approvals are also in progress in other regions.
Source: merck.com
