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Clesrovimab Receives FDA Approval for RSV Lower Respiratory Tract Prevention in Infants
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Key Takeaways
- Clesrovimab-cfor (Enflonsia) is FDA-approved for preventing RSV lower respiratory tract disease in infants during their first RSV season.
- The phase 2b/3 CLEVER trial showed significant reductions in RSV disease incidence and hospitalizations with clesrovimab.
The FDA approves clesrovimab-cfor, a new RSV vaccine, offering infants effective protection against severe respiratory illness during their first RSV season.
Coverage for this story is ongoing.
The FDA has approved clesrovimab-cfor (Enflonsia; Merck) for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in newborns and infants who are born during or entering their first RSV season. The approval is based on results from the phase 2b/3 CLEVER trial (NCT04767373) that evaluated a single dose of clesrovima administered to preterm and full-term infants, with ages ranging from birth to 1 year.1,2
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“RSV disease is the leading cause of infant hospitalization in the US and can lead to serious respiratory conditions like bronchiolitis and pneumonia,” said Octavio Ramilo, MD, chair of the department of infectious diseases at St. Jude Children’s Research Hospital and investigator for the CLEVER trial, in a news release. “[Clesrovimab] combines dosing convenience with strong clinical data showing significant reductions in RSV disease incidence and hospitalizations, making it a promising new intervention to help protect infants from RSV.”1
As a long-acting, preventive, monoclonal antibody, a 105 mg dose of clesrovimab is aimed to provide rapid and durable protection for a 5-month period, which is the typical duration of an RSV season, regardless of weight.1
REFERENCES
1. U.S. FDA Approves Merck’s ENFLONSIA™ (clesrovimab-cfor) for Prevention of Respiratory Syncytial Virus (RSV) Lower Respiratory Tract Disease in Infants Born During or Entering Their First RSV Season. Merck. News release. June 9, 2025. Accessed June 9, 2025. https://www.merck.com/news/u-s-fda-approves-mercks-enflonsia-clesrovimab-cfor-for-prevention-of-respiratory-syncytial-virus-rsv-lower-respiratory-tract-disease-in-infants-born-during-or-entering-their-fir/
2. Efficacy and Safety of Clesrovimab (MK-1654) in Infants (MK-1654-004) (CLEVER). ClinicalTrials.gov: NCT04767373. Updated May 6, 2025. Accessed June 9, 2025. https://clinicaltrials.gov/study/NCT04767373
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