Merck's ENFLONSIA Wins Positive EU CHMP Opinion to Expand to Vulnerable Children Up to 24 Months Through Their Second RSV Season
Merck, known as MSD outside the United States and Canada, announced on November 13 that the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency has adopted a positive opinion recommending that the marketing authorization for ENFLONSIA (clesrovimab) be expanded to include children up to 24 months of age who remain vulnerable to severe respiratory syncytial virus (RSV) disease through their second RSV season. The recommendation will now be reviewed by the European Commission, whose decision would apply across the European Union, Iceland, Liechtenstein and Norway. ENFLONSIA is a long-acting monoclonal antibody for the prevention of RSV lower respiratory tract disease, administered using the same dose regardless of weight.
The opinion is supported by the Phase 3 SMART trial (MK-1654-007), which enrolled infants and children at increased risk for severe RSV disease, including early and moderate preterm infants and children with chronic lung disease of prematurity or hemodynamically significant congenital heart disease, and compared ENFLONSIA with palivizumab. In the second RSV season, 276 eligible children under two years of age received an additional 210 mg dose of ENFLONSIA. Its safety was generally consistent with that observed in infants who received ENFLONSIA during their first RSV season, and antibody levels were similar to those in healthy infants in the pivotal CLEVER trial, supporting extrapolation of efficacy to this higher-risk population.
ENFLONSIA was approved by the U.S. Food and Drug Administration in June 2025 and by the European Commission in April 2026 for infants born during or entering their first RSV season, and it is now approved in more than 40 countries, including the United States, Canada, the European Union, China and Japan. The FDA has accepted a supplemental application for the same second-season expansion, with a target action date of March 22, 2027, and the European Medicines Agency accepted the EU application in July 2026. The CHMP positive opinion is the next step in that EU review.
Source: Merck
Published by GSM · USA (original Chinese edition)
Photo: 图：位于 South San Francisco 的默克研究实验室。Coolcaesar 摄，CC BY-SA 4.0，经 Wikimedia Commons。 / Photo: Merck Research Laboratories in South San Francisco, California. Photo by Coolcaesar, CC BY-SA 4.0, via Wikimedia Commons.
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